%%% -*-BibTeX-*- %%% ==================================================================== %%% BibTeX-file{ %%% author = "Nelson H. F. Beebe", %%% version = "1.10", %%% date = "29 August 2016", %%% time = "06:42:18 MDT", %%% filename = "teac.bib", %%% address = "University of Utah %%% Department of Mathematics, 110 LCB %%% 155 S 1400 E RM 233 %%% Salt Lake City, UT 84112-0090 %%% USA", %%% telephone = "+1 801 581 5254", %%% FAX = "+1 801 581 4148", %%% URL = "http://www.math.utah.edu/~beebe", %%% checksum = "59988 4187 23967 219964", %%% email = "beebe at math.utah.edu, beebe at acm.org, %%% beebe at computer.org (Internet)", %%% codetable = "ISO/ASCII", %%% keywords = "bibliography; BibTeX; ACM Transactions on %%% Economics and Computation (TEAC)", %%% license = "public domain", %%% supported = "no", %%% docstring = "This is a COMPLETE BibTeX bibliography for %%% the journal ACM Transactions on Economics and %%% Computation (no CODEN, ISSN 2167-8375 %%% (print), 2167-8383 (electronic)), for %%% 2013--date. %%% %%% Publication began with volume 1, number 1, %%% in January 2013. The journal appears %%% quarterly, in January, May, September, and %%% December. %%% %%% The journal has a World-Wide Web site at: %%% %%% http://teac.acm.org/ %%% %%% Tables-of-contents of all issues are %%% available at: %%% %%% http://dl.acm.org/citation.cfm?id=2542174 %%% %%% Qualified subscribers can retrieve the full %%% text of recent articles in PDF form. %%% %%% At version 1.10, the COMPLETE journal %%% coverage looked like this: %%% %%% 2013 ( 21) 2015 ( 32) %%% 2014 ( 17) 2016 ( 19) %%% %%% Article: 89 %%% %%% Total entries: 89 %%% %%% Spelling has been verified with the UNIX %%% spell and GNU ispell programs using the %%% exception dictionary stored in the %%% companion file with extension .sok. %%% %%% BibTeX citation tags are uniformly chosen %%% as name:year:abbrev, where name is the %%% family name of the first author or editor, %%% year is a 4-digit number, and abbrev is a %%% 3-letter condensation of important title %%% words. Citation tags were automatically %%% generated by software developed for the %%% BibNet Project. %%% %%% In this bibliography, entries are sorted in %%% publication order, using ``bibsort -byvolume.'' %%% %%% The checksum field above contains a CRC-16 %%% checksum as the first value, followed by the %%% equivalent of the standard UNIX wc (word %%% count) utility output of lines, words, and %%% characters. This is produced by Robert %%% Solovay's checksum utility.", %%% } %%% ====================================================================

@Preamble{"\input bibnames.sty"}

%%% ==================================================================== %%% Acknowledgement abbreviations:

@String{ack-nhfb= "Nelson H. F. Beebe, University of Utah, Department of Mathematics, 110 LCB, 155 S 1400 E RM 233, Salt Lake City, UT 84112-0090, USA, Tel: +1 801 581 5254, FAX: +1 801 581 4148, e-mail: \path|beebe@math.utah.edu|, \path|beebe@acm.org|, \path|beebe@computer.org| (Internet), URL: \path|http://www.math.utah.edu/~beebe/|"}

%%% ==================================================================== %%% Journal abbreviations:

@String{j-TEAC= "ACM Transactions on Economics and Computation"}

%%% ==================================================================== %%% Publisher abbreviations:

@String{pub-ACM= "ACM Press"} @String{pub-ACM:adr= "New York, NY 10036, USA"}

%%% ==================================================================== %%% Bibliography entries:

@Article{Conitzer:2013:ATE, author = "Vincent Conitzer and R. Preston Mcafee", title = "The {ACM Transactions on Economics and Computation}: an introduction", journal = j-TEAC, volume = "1", number = "1", pages = "1:1--1:??", month = jan, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2399187.2399188", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:51 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Gradwohl:2013:SRC, author = "Ronen Gradwohl and Noam Livne and Alon Rosen", title = "Sequential rationality in cryptographic protocols", journal = j-TEAC, volume = "1", number = "1", pages = "2:1--2:??", month = jan, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2399187.2399189", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:51 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/cryptography2010.bib; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Much of the literature on rational cryptography focuses on analyzing the strategic properties of cryptographic protocols. However, due to the presence of computationally-bounded players and the asymptotic nature of cryptographic security, a definition of sequential rationality for this setting has thus far eluded researchers. We propose a new framework for overcoming these obstacles, and provide the first definitions of computational solution concepts that guarantee sequential rationality. We argue that natural computational variants of subgame perfection are too strong for cryptographic protocols. As an alternative, we introduce a weakening called threat-free Nash equilibrium that is more permissive but still eliminates the undesirable ``empty threats'' of nonsequential solution concepts. To demonstrate the applicability of our framework, we revisit the problem of implementing a mediator for correlated equilibria [Dodis et al 2000], and propose a variant of their protocol that is sequentially rational for a nontrivial class of correlated equilibria. Our treatment provides a better understanding of the conditions under which mediators in a correlated equilibrium can be replaced by a stable protocol.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Jain:2013:GTA, author = "Shaili Jain and David C. Parkes", title = "A game-theoretic analysis of the {ESP} game", journal = j-TEAC, volume = "1", number = "1", pages = "3:1--3:??", month = jan, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2399187.2399190", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:51 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "``Games with a Purpose'' are interactive games that users play because they are fun, with the added benefit that the outcome of play is useful work. The ESP game, developed by von Ahn and Dabbish [2004], is an example of such a game devised to label images on the web. Since labeling images is a hard problem for computer vision algorithms and can be tedious and time-consuming for humans, the ESP game provides humans with incentive to do useful work by being enjoyable to play. We present a simple game-theoretic model of the ESP game and characterize the equilibrium behavior in our model. Our equilibrium analysis supports the fact that users appear to coordinate on low effort words. We provide an alternate model of user preferences, modeling a change that could be induced through a different scoring method, and show that equilibrium behavior in this model coordinates on high-effort words. We also give sufficient conditions for coordinating on high-effort words to be a Bayesian-Nash equilibrium. Our results suggest the possibility of formal incentive design in achieving desirable system-wide outcomes for the purpose of human computation, complementing existing considerations of robustness against cheating and human factors.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Naroditskiy:2013:OPD, author = "Victor Naroditskiy and Maria Polukarov and Nicholas R. Jennings", title = "Optimal payments in dominant-strategy mechanisms for single-parameter domains", journal = j-TEAC, volume = "1", number = "1", pages = "4:1--4:??", month = jan, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2399187.2399191", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:51 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study dominant-strategy mechanisms in allocation domains where agents have one-dimensional types and quasilinear utilities. Taking an allocation function as an input, we present an algorithmic technique for finding optimal payments in a class of mechanism design problems, including utilitarian and egalitarian allocation of homogeneous items with nondecreasing marginal costs. Our results link optimality of payment functions to a geometric condition involving triangulations of polytopes. When this condition is satisfied, we constructively show the existence of an optimal payment function that is piecewise linear in agent types.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Feldman:2013:ISI, author = "Michal Feldman and Noam Nisan", title = "Introduction to the {Special Issue on Algorithmic Game Theory}", journal = j-TEAC, volume = "1", number = "2", pages = "5:1--5:??", month = may, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2465769.2465770", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:52 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Blume:2013:NFP, author = "Lawrence Blume and David Easley and Jon Kleinberg and Robert Kleinberg and {\'E}va Tardos", title = "Network Formation in the Presence of Contagious Risk", journal = j-TEAC, volume = "1", number = "2", pages = "6:1--6:??", month = may, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2465769.2465771", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:52 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "There are a number of domains where agents must collectively form a network in the face of the following trade-off: each agent receives benefits from the direct links it forms to others, but these links expose it to the risk of being hit by a cascading failure that might spread over multistep paths. Financial contagion, epidemic disease, the exposure of covert organizations to discovery, and electrical power networks are all settings in which such issues have been articulated. Here we formulate the problem in terms of strategic network formation, and provide asymptotically tight bounds on the welfare of both optimal and stable networks. We find that socially optimal networks are, in a precise sense, situated just beyond a phase transition in the behavior of the cascading failures, and that stable graphs lie slightly further beyond this phase transition, at a point where most of the available welfare has been lost. Our analysis enables us to explore such issues as the trade-offs between clustered and anonymous market structures, and it exposes a fundamental sense in which very small amounts of ``over-linking'' in networks with contagious risk can have strong consequences for the welfare of the participants.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Karlin:2013:SEM, author = "Anna R. Karlin and C. Thach Nguyen and Yuval Peres", title = "Selling in Exclusive Markets: Some Observations on Prior-Free Mechanism Design", journal = j-TEAC, volume = "1", number = "2", pages = "7:1--7:??", month = may, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2465769.2465772", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:52 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider prior-free benchmarks in non-matroid settings. In particular, we show that a very desirable benchmark proposed by Hartline and Roughgarden is too strong, in the sense that no truthful mechanism can compete with it even in a very simple non-matroid setting where there are two exclusive markets and the seller can only sell to agents in one of them. On the other hand, we show that there is a mechanism that competes with a symmetrized version of this benchmark. We further investigate the more traditional best fixed price profit benchmark and show that there are mechanisms that compete with it in any downward-closed settings.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Ha:2013:MDC, author = "Bach Q. Ha and Jason D. Hartline", title = "Mechanism Design via Consensus Estimates, Cross Checking, and Profit Extraction", journal = j-TEAC, volume = "1", number = "2", pages = "8:1--8:??", month = may, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2465769.2465773", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:52 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "There is only one technique for prior-free optimal mechanism design that generalizes beyond the structurally benevolent setting of digital goods. This technique uses random sampling to estimate the distribution of agent values and then employs the Bayesian optimal mechanism for this estimated distribution on the remaining players. Though quite general, even for digital goods, this random sampling auction has a complicated analysis and is known to be suboptimal. To overcome these issues we generalize the consensus and profit extraction techniques from Goldberg and Hartline [2003] to structurally rich environments that include, for example, single-minded combinatorial auctions.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Goldberg:2013:CHM, author = "Paul W. Goldberg and Christos H. Papadimitriou and Rahul Savani", title = "The Complexity of the Homotopy Method, Equilibrium Selection, and {Lemke--Howson} Solutions", journal = j-TEAC, volume = "1", number = "2", pages = "9:1--9:??", month = may, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2465769.2465774", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:52 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We show that the widely used homotopy method for solving fixpoint problems, as well as the Harsanyi-Selten equilibrium selection process for games, are PSPACE-complete to implement. Extending our result for the Harsanyi-Selten process, we show that several other homotopy-based algorithms for finding equilibria of games are also PSPACE-complete to implement. A further application of our techniques yields the result that it is PSPACE-complete to compute any of the equilibria that could be found via the classical Lemke--Howson algorithm, a complexity-theoretic strengthening of the result in Savani and von Stengel [2006]. These results show that our techniques can be widely applied and suggest that the PSPACE-completeness of implementing homotopy methods is a general principle.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Koutsoupias:2013:CRO, author = "Elias Koutsoupias and George Pierrakos", title = "On the Competitive Ratio of Online Sampling Auctions", journal = j-TEAC, volume = "1", number = "2", pages = "10:1--10:??", month = may, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2465769.2465775", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:52 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study online profit-maximizing auctions for digital goods with adversarial bid selection and uniformly random arrivals; in this sense, our model lies at the intersection of prior-free mechanism design and secretary problems. Our goal is to design auctions that are constant competitive with F$^{(2)}$. We give a generic reduction that transforms any offline auction to an online one with only a loss of a factor of 2 in the competitive ratio. We also present some natural auctions, both randomized and deterministic, and study their competitive ratio. Our analysis reveals some interesting connections of one of these auctions with RSOP.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Candogan:2013:NPG, author = "Ozan Candogan and Asuman Ozdaglar and Pablo A. Parrilo", title = "Near-Potential Games: Geometry and Dynamics", journal = j-TEAC, volume = "1", number = "2", pages = "11:1--11:??", month = may, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2465769.2465776", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:52 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Potential games are a special class of games for which many adaptive user dynamics converge to a Nash equilibrium. In this article, we study properties of near-potential games, that is, games that are close in terms of payoffs to potential games, and show that such games admit similar limiting dynamics. We first focus on finite games in strategic form. We introduce a distance notion in the space of games and study the geometry of potential games and sets of games that are equivalent, with respect to various equivalence relations, to potential games. We discuss how, given an arbitrary game, one can find a nearby game in these sets. We then study dynamics in near-potential games by focusing on continuous-time perturbed best response dynamics. We characterize the limiting behavior of this dynamics in terms of the upper contour sets of the potential function of a close potential game and approximate equilibria of the game. Exploiting structural properties of approximate equilibrium sets, we strengthen our result and show that for games that are sufficiently close to a potential game, the sequence of mixed strategies generated by this dynamics converges to a small neighborhood of equilibria whose size is a function of the distance from the set of potential games. In the second part of the article, we study continuous games and show that our approach for characterizing the limiting sets in near-potential games extends to continuous games. In particular, we consider continuous-time best response dynamics and a variant of it (where players update their strategies only if there is at least $ \epsilon $ utility improvement opportunity) in near-potential games where the strategy sets are compact and convex subsets of a Euclidean space. We show that these update rules converge to a neighborhood of equilibria (or the maximizer of the potential function), provided that the potential function of the nearby potential game satisfies some structural properties. Our results generalize the known convergence results for potential games to near-potential games.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Abernethy:2013:EMM, author = "Jacob Abernethy and Yiling Chen and Jennifer Wortman Vaughan", title = "Efficient Market Making via Convex Optimization, and a Connection to Online Learning", journal = j-TEAC, volume = "1", number = "2", pages = "12:1--12:??", month = may, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2465769.2465777", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:52 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We propose a general framework for the design of securities markets over combinatorial or infinite state or outcome spaces. The framework enables the design of computationally efficient markets tailored to an arbitrary, yet relatively small, space of securities with bounded payoff. We prove that any market satisfying a set of intuitive conditions must price securities via a convex cost function, which is constructed via conjugate duality. Rather than deal with an exponentially large or infinite outcome space directly, our framework only requires optimization over a convex hull. By reducing the problem of automated market making to convex optimization, where many efficient algorithms exist, we arrive at a range of new polynomial-time pricing mechanisms for various problems. We demonstrate the advantages of this framework with the design of some particular markets. We also show that by relaxing the convex hull we can gain computational tractability without compromising the market institution's bounded budget. Although our framework was designed with the goal of deriving efficient automated market makers for markets with very large outcome spaces, this framework also provides new insights into the relationship between market design and machine learning, and into the complete market setting. Using our framework, we illustrate the mathematical parallels between cost-function-based markets and online learning and establish a correspondence between cost-function-based markets and market scoring rules for complete markets.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Haghpanah:2013:OAP, author = "Nima Haghpanah and Nicole Immorlica and Vahab Mirrokni and Kamesh Munagala", title = "Optimal Auctions with Positive Network Externalities", journal = j-TEAC, volume = "1", number = "2", pages = "13:1--13:??", month = may, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2465769.2465778", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:52 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider the problem of designing auctions in social networks for goods that exhibit single-parameter submodular network externalities in which a bidder's value for an outcome is a fixed private type times a known submodular function of the allocation of his friends. Externalities pose many issues that are hard to address with traditional techniques; our work shows how to resolve these issues in a specific setting of particular interest. We operate in a Bayesian environment and so assume private values are drawn according to known distributions. We prove that the optimal auction is NP-hard to approximate pointwise, and APX-hard on average. Thus we instead design auctions whose revenue approximates that of the optimal auction. Our main result considers step-function externalities in which a bidder's value for an outcome is either zero, or equal to his private type if at least one friend has the good. For these settings, we provide a e / e + 1-approximation. We also give a 0.25-approximation auction for general single-parameter submodular network externalities, and discuss optimizing over a class of simple pricing strategies.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Othman:2013:PLS, author = "Abraham Othman and David M. Pennock and Daniel M. Reeves and Tuomas Sandholm", title = "A Practical Liquidity-Sensitive Automated Market Maker", journal = j-TEAC, volume = "1", number = "3", pages = "14:1--14:??", month = sep, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2509413.2509414", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:54 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Automated market makers are algorithmic agents that enable participation and information elicitation in electronic markets. They have been widely and successfully applied in artificial-money settings, like some Internet prediction markets. Automated market makers from the literature suffer from two problems that contribute to their impracticality and impair their use beyond artificial-money settings: first, they are unable to adapt to liquidity, so that trades cause prices to move the same amount in both heavily and lightly traded markets, and second, in typical circumstances, they run at a deficit. In this article, we construct a market maker that is both sensitive to liquidity and can run at a profit. Our market maker has bounded loss for any initial level of liquidity and, as the initial level of liquidity approaches zero, worst-case loss approaches zero. For any level of initial liquidity we can establish a boundary in market state space such that, if the market terminates within that boundary, the market maker books a profit regardless of the realized outcome.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Balcan:2013:PU, author = "Maria-Florina Balcan and Avrim Blum and Yishay Mansour", title = "The Price of Uncertainty", journal = j-TEAC, volume = "1", number = "3", pages = "15:1--15:??", month = sep, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2509413.2509415", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:54 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "In this work, we study the degree to which small fluctuations in costs in well-studied potential games can impact the result of natural best-response and improved-response dynamics. We call this the Price of Uncertainty and study it in a wide variety of potential games including fair cost-sharing games, set-cover games, routing games, and job-scheduling games. We show that in certain cases, even extremely small fluctuations can have the ability to cause these dynamics to spin out of control and move to states of much higher social cost, whereas in other cases these dynamics are much more stable even to large degrees of fluctuation. We also consider the resilience of these dynamics to a small number of Byzantine players about which no assumptions are made. We show again a contrast between different games. In certain cases (e.g., fair cost-sharing, set-cover, job-scheduling) even a single Byzantine player can cause best-response dynamics to transition from low-cost states to states of substantially higher cost, whereas in others (e.g., the class of $ \beta $-nice games, which includes routing, market-sharing and many others) these dynamics are much more resilient. Overall, our work can be viewed as analyzing the inherent resilience or safety of games to different kinds of imperfections in player behavior, player information, or in modeling assumptions made.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Ben-Yehuda:2013:DAE, author = "Orna Agmon Ben-Yehuda and Muli Ben-Yehuda and Assaf Schuster and Dan Tsafrir", title = "Deconstructing {Amazon EC2} Spot Instance Pricing", journal = j-TEAC, volume = "1", number = "3", pages = "16:1--16:??", month = sep, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2509413.2509416", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:54 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Cloud providers possessing large quantities of spare capacity must either incentivize clients to purchase it or suffer losses. Amazon is the first cloud provider to address this challenge, by allowing clients to bid on spare capacity and by granting resources to bidders while their bids exceed a periodically changing spot price. Amazon publicizes the spot price but does not disclose how it is determined. By analyzing the spot price histories of Amazon's EC2 cloud, we reverse engineer how prices are set and construct a model that generates prices consistent with existing price traces. Our findings suggest that usually prices are not market-driven, as sometimes previously assumed. Rather, they are likely to be generated most of the time at random from within a tight price range via a dynamic hidden reserve price mechanism. Our model could help clients make informed bids, cloud providers design profitable systems, and researchers design pricing algorithms.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Sarne:2013:CSM, author = "David Sarne", title = "Competitive Shopbots-Mediated Markets", journal = j-TEAC, volume = "1", number = "3", pages = "17:1--17:??", month = sep, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2509413.2509417", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:54 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "This article considers markets mediated by autonomous self-interested comparison-shopping agents. As in today's markets, the agents do not charge buyers for their services but rather benefit from payments obtained from sellers upon the execution of a transaction. The agents aim at maximizing their expected benefit, taking into consideration the cost incurred by the search and competition dynamics that arise in the multi-agent setting. This article provides a comprehensive analysis of such models, based on search theory principles. The analysis results in a characterization of the buyers' and agents' search strategies in equilibrium. The main result of this article is that the use of self-interested comparison-shopping agents can result in a beneficial equilibrium, where both buyers and sellers benefit, in comparison to the case where buyers control the comparison-shopping agent, and the comparison-shopping agents necessarily do not lose. This, despite the fact that the service is offered for free to buyers and its cost is essentially covered by sellers. The analysis generalizes to any setting where buyers can use self-interested agents capable of effectively performing the search (e.g., evaluating opportunities) on their behalf.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Procaccia:2013:AMD, author = "Ariel D. Procaccia and Moshe Tennenholtz", title = "Approximate Mechanism Design without Money", journal = j-TEAC, volume = "1", number = "4", pages = "18:1--18:??", month = dec, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2542174.2542175", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:56 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "The literature on algorithmic mechanism design is mostly concerned with game-theoretic versions of optimization problems to which standard economic money-based mechanisms cannot be applied efficiently. Recent years have seen the design of various truthful approximation mechanisms that rely on payments. In this article, we advocate the reconsideration of highly structured optimization problems in the context of mechanism design. We explicitly argue for the first time that, in such domains, approximation can be leveraged to obtain truthfulness without resorting to payments. This stands in contrast to previous work where payments are almost ubiquitous and (more often than not) approximation is a necessary evil that is required to circumvent computational complexity. We present a case study in approximate mechanism design without money. In our basic setting, agents are located on the real line and the mechanism must select the location of a public facility; the cost of an agent is its distance to the facility. We establish tight upper and lower bounds for the approximation ratio given by strategy-proof mechanisms without payments, with respect to both deterministic and randomized mechanisms, under two objective functions: the social cost and the maximum cost. We then extend our results in two natural directions: a domain where two facilities must be located and a domain where each agent controls multiple locations.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Yildiz:2013:BOD, author = "Ercan Yildiz and Asuman Ozdaglar and Daron Acemoglu and Amin Saberi and Anna Scaglione", title = "Binary Opinion Dynamics with Stubborn Agents", journal = j-TEAC, volume = "1", number = "4", pages = "19:1--19:??", month = dec, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2538508", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:56 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study binary opinion dynamics in a social network with stubborn agents who influence others but do not change their opinions. We focus on a generalization of the classical voter model by introducing nodes (stubborn agents) that have a fixed state. We show that the presence of stubborn agents with opposing opinions precludes convergence to consensus; instead, opinions converge in distribution with disagreement and fluctuations. In addition to the first moment of this distribution typically studied in the literature, we study the behavior of the second moment in terms of network properties and the opinions and locations of stubborn agents. We also study the problem of optimal placement of stubborn agents where the location of a fixed number of stubborn agents is chosen to have the maximum impact on the long-run expected opinions of agents.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Mossel:2013:MCT, author = "Elchanan Mossel and Omer Tamuz", title = "Making Consensus Tractable", journal = j-TEAC, volume = "1", number = "4", pages = "20:1--20:??", month = dec, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2542174.2542176", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:56 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study a model of consensus decision making in which a finite group of Bayesian agents has to choose between one of two courses of action. Each member of the group has a private and independent signal at his or her disposal, giving some indication as to which action is optimal. To come to a common decision, the participants perform repeated rounds of voting. In each round, each agent casts a vote in favor of one of the two courses of action, reflecting his or her current belief, and observes the votes of the rest. We provide an efficient algorithm for the calculation the agents have to perform and show that consensus is always reached and that the probability of reaching a wrong decision decays exponentially with the number of agents.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Hoefer:2013:AAC, author = "Martin Hoefer and Alexander Skopalik", title = "Altruism in Atomic Congestion Games", journal = j-TEAC, volume = "1", number = "4", pages = "21:1--21:??", month = dec, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2542174.2542177", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 14 06:10:56 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "This article studies the effects of altruism, a phenomenon widely observed in practice, in the model of atomic congestion games. Altruistic behavior is modeled by a linear trade-off between selfish and social objectives. Our model can be embedded in the framework of congestion games with player-specific latency functions. Stable states are the pure Nash equilibria of these games, and we examine their existence and the convergence of sequential best-response dynamics. In general, pure Nash equilibria are often absent, and existence is NP-hard to decide. Perhaps surprisingly, if all delay functions are affine, the games remain potential games, even when agents are arbitrarily altruistic. The construction underlying this result can be extended to a class of general potential games and social cost functions, and we study a number of prominent examples. These results give important insights into the robustness of multi-agent systems with heterogeneous altruistic incentives. Furthermore, they yield a general technique to prove that stabilization is robust, even with partly altruistic agents, which is of independent interest. In addition to these results for uncoordinated dynamics, we consider a scenario with a central altruistic institution that can set incentives for the agents. We provide constructive and hardness results for finding the minimum number of altruists to stabilize an optimal congestion profile and more general mechanisms to incentivize agents to adopt favorable behavior. These results are closely related to Stackelberg routing and answer open questions raised recently in the literature.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Polevoy:2014:SCS, author = "Gleb Polevoy and Rann Smorodinsky and Moshe Tennenholtz", title = "Signaling Competition and Social Welfare", journal = j-TEAC, volume = "2", number = "1", pages = "1:1--1:??", month = mar, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2560766", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 21 18:00:43 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider an environment where sellers compete over buyers. All sellers are a-priori identical and strategically signal buyers about the product they sell. In a setting motivated by online advertising in display ad exchanges, where firms use second price auctions, a firm's strategy is a decision about its signaling scheme for a stream of goods (e.g., user impressions), and a buyer's strategy is a selection among the firms. In this setting, a single seller will typically provide partial information, and consequently, a product may be allocated inefficiently. Intuitively, competition among sellers may induce sellers to provide more information in order to attract buyers and thus increase efficiency. Surprisingly, we show that such a competition among firms may yield significant loss in consumers' social welfare with respect to the monopolistic setting. Although we also show that in some cases, the competitive setting yields gain in social welfare, we provide a tight bound on that gain, which is shown to be small with respect to the preceding possible loss. Our model is tightly connected with the literature on bundling in auctions.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Albers:2014:NEN, author = "Susanne Albers and Stefan Eilts and Eyal Even-Dar and Yishay Mansour and Liam Roditty", title = "On {Nash} Equilibria for a Network Creation Game", journal = j-TEAC, volume = "2", number = "1", pages = "2:1--2:??", month = mar, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2560767", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 21 18:00:43 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study a basic network creation game proposed by Fabrikant et al. [2003]. In this game, each player (vertex) can create links (edges) to other players at a cost of \alpha per edge. The goal of every player is to minimize the sum consisting of (a) the cost of the links he has created and (b) the sum of the distances to all other players. Fabrikant et al. conjectured that there exists a constant $A$ such that, for any $\alpha > A$, all nontransient Nash equilibria graphs are trees. They showed that if a Nash equilibrium is a tree, the price of anarchy is constant. In this article, we disprove the tree conjecture. More precisely, we show that for any positive integer $n_0$, there exists a graph built by $n \geq n_0$ players which contains cycles and forms a nontransient Nash equilibrium, for any $\alpha$ with $1 < \alpha \leq \sqrt n / 2$. Our construction makes use of some interesting results on finite affine planes. On the other hand, we show that, for $\alpha \geq 12 n \lceil log n \rceil$, every Nash equilibrium forms a tree. Without relying on the tree conjecture, Fabrikant et al. proved an upper bound on the price of anarchy of $O(\sqrt{\alpha})$, where $\alpha \in [2, n^2]$. We improve this bound. Specifically, we derive a constant upper bound for $\alpha \in O(\sqrt{n})$ and for $\alpha \geq 12 n \lceil log n \rceil$. For the intermediate values, we derive an improved bound of $O(1 + (\min\{\alpha^2 / n, n^2 / \alpha \})^{1 / 3})$. Additionally, we develop characterizations of Nash equilibria and extend our results to a weighted network creation game as well as to scenarios with cost sharing.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Smeulders:2014:GFM, author = "Bart Smeulders and Frits C. R. Spieksma and Laurens Cherchye and Bram {De Rock}", title = "Goodness-of-Fit Measures for Revealed Preference Tests: Complexity Results and Algorithms", journal = j-TEAC, volume = "2", number = "1", pages = "3:1--3:??", month = mar, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2560793", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 21 18:00:43 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We provide results on the computational complexity of goodness-of-fit measures (i.e., Afriat's efficiency index, Varian's efficiency vector-index, and the Houtman-Maks index) associated with several revealed preference axioms (i.e., WARP, SARP, GARP, and HARP). These results explain the computational difficulties that have been observed in literature when computing these indices. Our NP-hardness results are obtained by reductions from the independent set problem. We also show that this reduction can be used to prove that no approximation algorithm achieving a ratio of $O(n^{1 - \delta})$, $\delta;> 0$ exists for Varian's index, nor for Houtman-Maks' index (unless P = NP). Finally, we give an exact polynomial-time algorithm for finding Afriat's efficiency index.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Zhang:2014:RPO, author = "Yu Zhang and Jaeok Park and Mihaela van der Schaar", title = "Rating Protocols in Online Communities", journal = j-TEAC, volume = "2", number = "1", pages = "4:1--4:??", month = mar, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2560794", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 21 18:00:43 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Sustaining cooperation among self-interested agents is critical for the proliferation of emerging online communities. Providing incentives for cooperation in online communities is particularly challenging because of their unique features: a large population of anonymous agents having asymmetric interests and dynamically joining and leaving the community, operation errors, and agents trying to whitewash when they have a low standing in the community. In this article, we take these features into consideration and propose a framework for designing and analyzing a class of incentive schemes based on rating protocols, which consist of a rating scheme and a recommended strategy. We first define the concept of sustainable rating protocols under which every agent has the incentive to follow the recommended strategy given the deployed rating scheme. We then formulate the problem of designing an optimal rating protocol, which selects the protocol that maximizes the overall social welfare among all sustainable rating protocols. Using the proposed framework, we study the structure of optimal rating protocols and explore the impact of one-sided rating, punishment lengths, and whitewashing on optimal rating protocols. Our results show that optimal rating protocols are capable of sustaining cooperation, with the amount of cooperation varying depending on the community characteristics.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Emek:2014:SSR, author = "Yuval Emek and Michal Feldman and Iftah Gamzu and Renato PaesLeme and Moshe Tennenholtz", title = "Signaling Schemes for Revenue Maximization", journal = j-TEAC, volume = "2", number = "2", pages = "5:1--5:??", month = jun, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2594564", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Jun 9 16:42:02 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Signaling is an important topic in the study of asymmetric information in economic settings. In particular, the transparency of information available to a seller in an auction setting is a question of major interest. We introduce the study of signaling when conducting a second price auction of a probabilistic good whose actual instantiation is known to the auctioneer but not to the bidders. This framework can be used to model impressions selling in display advertising. We establish several results within this framework. First, we study the problem of computing a signaling scheme that maximizes the auctioneer's revenue in a Bayesian setting. We show that this problem is polynomially solvable for some interesting special cases, but computationally hard in general. Second, we establish a tight bound on the minimum number of signals required to implement an optimal signaling scheme. Finally, we show that at least half of the maximum social welfare can be preserved within such a scheme.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Chen:2014:EPR, author = "Yiling Chen and Ian A. Kash and Michael Ruberry and Victor Shnayder", title = "Eliciting Predictions and Recommendations for Decision Making", journal = j-TEAC, volume = "2", number = "2", pages = "6:1--6:??", month = jun, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2556271", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Jun 9 16:42:02 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "When making a decision, a decision maker selects one of several possible actions and hopes to achieve a desirable outcome. To make a better decision, the decision maker often asks experts for advice. In this article, we consider two methods of acquiring advice for decision making. We begin with a method where one or more experts predict the effect of each action and the decision maker then selects an action based on the predictions. We characterize strictly proper decision making, where experts have an incentive to accurately reveal their beliefs about the outcome of each action. However, strictly proper decision making requires the decision maker use a completely mixed strategy to choose an action. To address this limitation, we consider a second method where the decision maker asks a single expert to recommend an action. We show that it is possible to elicit the decision maker's most preferred action for a broad class of preferences of the decision maker, including when the decision maker is an expected value maximizer.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Rozen:2014:EPE, author = "Rakefet Rozen and Rann Smorodinsky", title = "Ex-Post Equilibrium and {VCG} Mechanisms", journal = j-TEAC, volume = "2", number = "2", pages = "7:1--7:??", month = jun, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2594565", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Jun 9 16:42:02 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Consider an abstract social choice setting with incomplete information, where the number of alternatives is large. Albeit natural, implementing VCG mechanisms is infeasible due to the prohibitive communication constraints. However, if players restrict attention to a subset of the alternatives, feasibility may be recovered. This article characterizes the class of subsets that induce an ex-post equilibrium in the original game. It turns out that a crucial condition for such subsets to exist is the availability of a type-independent optimal social alternative for each player. We further analyze the welfare implications of these restrictions. This work follows that of Holzman et al. [2004] and Holzman and Monderer [2004] where similar analysis is done for combinatorial auctions.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Chen:2014:PAS, author = "Xujin Chen and Benjamin Doerr and Carola Doerr and Xiaodong Hu and Weidong Ma and Rob van Stee", title = "The Price of Anarchy for Selfish Ring Routing is Two", journal = j-TEAC, volume = "2", number = "2", pages = "8:1--8:??", month = jun, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2548545", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Jun 9 16:42:02 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We analyze the network congestion game with atomic players, asymmetric strategies, and the maximum latency among all players as social cost. This important social cost function is much less understood than the average latency. We show that the price of anarchy is at most two, when the network is a ring and the link latencies are linear. Our bound is tight. This is the first sharp bound for the maximum latency objective.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Cary:2014:CPA, author = "Matthew Cary and Aparna Das and Benjamin Edelman and Ioannis Giotis and Kurtis Heimerl and Anna R. Karlin and Scott Duke Kominers and Claire Mathieu and Michael Schwarz", title = "Convergence of Position Auctions under Myopic Best-Response Dynamics", journal = j-TEAC, volume = "2", number = "3", pages = "9:1--9:??", month = jul, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2632226", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Oct 17 12:45:12 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study the dynamics of multiround position auctions, considering both the case of exogenous click-through rates and the case in which click-through rates are determined by an endogenous consumer search process. In both contexts, we demonstrate that dynamic position auctions converge to their associated static, envy-free equilibria. Furthermore, convergence is efficient, and the entry of low-quality advertisers does not slow convergence. Because our approach predominantly relies on assumptions common in the sponsored search literature, our results suggest that dynamic position auctions converge more generally.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Azar:2014:QCS, author = "Pablo Daniel Azar and Silvio Micali", title = "The Query Complexity of Scoring Rules", journal = j-TEAC, volume = "2", number = "3", pages = "10:1--10:??", month = jul, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2632228", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Oct 17 12:45:12 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Proper scoring rules are crucial tools to elicit truthful information from experts. A scoring rule maps X, an expert-provided distribution over the set of all possible states of the world, and $ \omega $, a realized state of the world, to a real number representing the expert's reward for his provided information. To compute this reward, a scoring rule queries the distribution X at various states. The number of these queries is thus a natural measure of the complexity of the scoring rule. We prove that any bounded and strictly proper scoring rule that is deterministic must make a number of queries to its input distribution that is a quarter of the number of states of the world. When the state space is very large, this makes the computation of such scoring rules impractical. We also show a new stochastic scoring rule that is bounded, strictly proper, and which makes only two queries to its input distribution. Thus, using randomness allows us to have significant savings when computing scoring rules.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Alaei:2014:RSA, author = "Saeed Alaei and Azarakhsh Malekian and Aravind Srinivasan", title = "On Random Sampling Auctions for Digital Goods", journal = j-TEAC, volume = "2", number = "3", pages = "11:1--11:??", month = jul, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2517148", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Oct 17 12:45:12 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "In the context of auctions for digital goods, an interesting random sampling auction has been proposed by Goldberg et al. [2001]. This auction has been analyzed by Feige et al. [2005], who have shown that it obtains in expectation at least 1/15 fraction of the optimal revenue, which is substantially better than the previously proven constant bounds but still far from the conjectured lower bound of 1/4. In this article, we prove that the aforementioned random sampling auction obtains at least 1/4 fraction of the optimal revenue for a large class of instances where the number of bids above (or equal to) the optimal sale price is at least 6. We also show that this auction obtains at least 1/4.68 fraction of the optimal revenue for the small class of remaining instances, thus leaving a negligible gap between the lower and upper bound. We employ a mix of probabilistic techniques and dynamic programming to compute these bounds.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Dandekar:2014:PAR, author = "Pranav Dandekar and Nadia Fawaz and Stratis Ioannidis", title = "Privacy Auctions for Recommender Systems", journal = j-TEAC, volume = "2", number = "3", pages = "12:1--12:??", month = jul, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629665", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Oct 17 12:45:12 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study a market for private data in which a data analyst publicly releases a statistic over a database of private information. Individuals that own the data incur a cost for their loss of privacy proportional to the differential privacy guarantee given by the analyst at the time of the release. The analyst incentivizes individuals by compensating them, giving rise to a privacy auction. Motivated by recommender systems, the statistic we consider is a linear predictor function with publicly known weights. The statistic can be viewed as a prediction of the unknown data of a new individual, based on the data of individuals in the database. We formalize the trade-off between privacy and accuracy in this setting, and show that a simple class of estimates achieves an order-optimal trade-off. It thus suffices to focus on auction mechanisms that output such estimates. We use this observation to design a truthful, individually rational, proportional-purchase mechanism under a fixed budget constraint. We show that our mechanism is 5-approximate in terms of accuracy compared to the optimal mechanism, and that no truthful mechanism can achieve a $ 2 - \epsilon $ approximation, for any $\epsilon > 0$.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Balcan:2014:NOC, author = "Maria-Florina Balcan and Sara Krehbiel and Georgios Piliouras and Jinwoo Shin", title = "Near-Optimality in Covering Games by Exposing Global Information", journal = j-TEAC, volume = "2", number = "4", pages = "13:1--13:??", month = oct, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2597890", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Oct 28 16:50:26 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Mechanism design for distributed systems is fundamentally concerned with aligning individual incentives with social welfare to avoid socially inefficient outcomes that can arise from agents acting autonomously. One simple and natural approach is to centrally broadcast nonbinding advice intended to guide the system to a socially near-optimal state while still harnessing the incentives of individual agents. The analytical challenge is proving fast convergence to near optimal states, and in this article we give the first results that carefully constructed advice vectors yield stronger guarantees. We apply this approach to a broad family of potential games modeling vertex cover and set cover optimization problems in a distributed setting. This class of problems is interesting because finding exact solutions to their optimization problems is NP-hard yet highly inefficient equilibria exist, so a solution in which agents simply locally optimize is not satisfactory. We show that with an arbitrary advice vector, a set cover game quickly converges to an equilibrium with cost of the same order as the square of the social cost of the advice vector. More interestingly, we show how to efficiently construct an advice vector with a particular structure with cost O (log n ) times the optimal social cost, and we prove that the system quickly converges to an equilibrium with social cost of this same order.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Bhawalkar:2014:WCG, author = "Kshipra Bhawalkar and Martin Gairing and Tim Roughgarden", title = "Weighted Congestion Games: The Price of Anarchy, Universal Worst-Case Examples, and Tightness", journal = j-TEAC, volume = "2", number = "4", pages = "14:1--14:??", month = oct, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629666", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Oct 28 16:50:26 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We characterize the Price of Anarchy (POA) in weighted congestion games, as a function of the allowable resource cost functions. Our results provide as thorough an understanding of this quantity as is already known for nonatomic and unweighted congestion games, and take the form of universal (cost function-independent) worst-case examples. One noteworthy by-product of our proofs is the fact that weighted congestion games are ``tight,'' which implies that the worst-case price of anarchy with respect to pure Nash equilibria, mixed Nash equilibria, correlated equilibria, and coarse correlated equilibria are always equal (under mild conditions on the allowable cost functions). Another is the fact that, like nonatomic but unlike atomic (unweighted) congestion games, weighted congestion games with trivial structure already realize the worst-case POA, at least for polynomial cost functions. We also prove a new result about unweighted congestion games: the worst-case price of anarchy in symmetric games is as large as in their more general asymmetric counterparts.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Fotakis:2014:PDM, author = "Dimitris Fotakis and Christos Tzamos", title = "On the Power of Deterministic Mechanisms for Facility Location Games", journal = j-TEAC, volume = "2", number = "4", pages = "15:1--15:??", month = oct, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2665005", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Oct 28 16:50:26 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider $K$-Facility Location games, where n strategic agents report their locations in a metric space and a mechanism maps them to $K$ facilities. The agents seek to minimize their connection cost, namely the distance of their true location to the nearest facility, and may misreport their location. We are interested in deterministic mechanisms that are strategyproof, that is, ensure that no agent can benefit from misreporting her location, do not resort to monetary transfers, and achieve a bounded approximation ratio to the total connection cost of the agents (or to the $ L_p $ norm of the connection costs, for some $ p \in [1, \infty) $ or for $ p = \infty) $. Our main result is an elegant characterization of deterministic strategyproof mechanisms with a bounded approximation ratio for $2$-Facility Location on the line. In particular, we show that for instances with $ n \geq 5 $ agents, any such mechanism either admits a unique dictator or always places the facilities at the leftmost and the rightmost location of the instance. As a corollary, we obtain that the best approximation ratio achievable by deterministic strategyproof mechanisms for the problem of locating $2$ facilities on the line to minimize the total connection cost is precisely $ n - 2$. Another rather surprising consequence is that the Two-Extremes mechanism of Procaccia and Tennenholtz [2009] is the only deterministic anonymous strategyproof mechanism with a bounded approximation ratio for $2$-Facility Location on the line. The proof of the characterization employs several new ideas and technical tools, which provide new insights into the behavior of deterministic strategyproof mechanisms for $K$-Facility Location games and may be of independent interest. Employing one of these tools, we show that for every $ K \geq 3$, there do not exist any deterministic anonymous strategyproof mechanisms with a bounded approximation ratio for $K$-Facility Location on the line, even for simple instances with $ K + 1$ agents. Moreover, building on the characterization for the line, we show that there do not exist any deterministic strategy proof mechanisms with a bounded approximation ratio for $2$-Facility Location and instances with $ n \geq 3$ agents located in a star.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Michalak:2014:ICV, author = "Tomasz P. Michalak and Piotr L. Szczepa{\'n}ski and Talal Rahwan and Agata Chrobak and Simina Br{\^a}nzei and Michael Wooldridge and Nicholas R. Jennings", title = "Implementation and Computation of a Value for Generalized Characteristic Function Games", journal = j-TEAC, volume = "2", number = "4", pages = "16:1--16:??", month = oct, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2665007", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Oct 28 16:50:26 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Generalized characteristic function games are a variation of characteristic function games, in which the value of a coalition depends not only on the identities of its members, but also on the order in which the coalition is formed. This class of games is a useful abstraction for a number of realistic settings and economic situations, such as modeling relationships in social networks. To date, two main extensions of the Shapley value have been proposed for generalized characteristic function games: the Nowak--Radzik [1994] value and the S{\'a}nchez--Berganti{\~n}os [1997] value. In this context, the present article studies generalized characteristic function games from the point of view of implementation and computation. Specifically, the article makes two key contributions. First, building upon the mechanism by Dasgupta and Chiu [1998], we present a non-cooperative mechanism that implements both the Nowak--Radzik value and the S{\'a}nchez-Berganti{\~n}os value in Subgame-Perfect Nash Equilibria in expectations. Second, in order to facilitate an efficient computation supporting the implementation mechanism, we propose the Generalized Marginal-Contribution Nets representation for this type of game. This representation extends the results of Ieong and Shoham [2005] and Elkind et al. [2009] for characteristic function games and retains their attractive computational properties.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Chen:2014:AIP, author = "Po-An Chen and Bart {De Keijzer} and David Kempe and Guido Sch{\"a}fer", title = "Altruism and Its Impact on the Price of Anarchy", journal = j-TEAC, volume = "2", number = "4", pages = "17:1--17:??", month = oct, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2597893", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Oct 28 16:50:26 MDT 2014", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study the inefficiency of equilibria for congestion games when players are (partially) altruistic. We model altruistic behavior by assuming that player $i$'s perceived cost is a convex combination of $\alpha_i$ times his direct cost and $\alpha_i$ times the social cost. Tuning the parameters $\alpha_i$ allows smooth interpolation between purely selfish and purely altruistic behavior. Within this framework, we study primarily altruistic extensions of (atomic and nonatomic) congestion games, but also obtain some results on fair cost-sharing games and valid utility games. We derive (tight) bounds on the price of anarchy of these games for several solution concepts. Thereto, we suitably adapt the smoothness notion introduced by Roughgarden and show that it captures the essential properties to determine the robust price of anarchy of these games. Our bounds show that for atomic congestion games and cost-sharing games, the robust price of anarchy gets worse with increasing altruism, while for valid utility games, it remains constant and is not affected by altruism. However, the increase in the price of anarchy is not a universal phenomenon: For general nonatomic congestion games with uniform altruism, the price of anarchy improves with increasing altruism. For atomic and nonatomic symmetric singleton congestion games, we derive bounds on the pure price of anarchy that improve as the average level of altruism increases. (For atomic games, we only derive such bounds when cost functions are linear.) Since the bounds are also strictly lower than the robust price of anarchy, these games exhibit natural examples in which pure Nash equilibria are more efficient than more permissive notions of equilibrium.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Leyton-Brown:2015:ISI, author = "Kevin Leyton-Brown and Panos Ipeirotis", title = "Introduction to the Special Issue on {EC'12}", journal = j-TEAC, volume = "3", number = "1", pages = "1:1--1:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2742678", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 27 17:58:56 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Caragiannis:2015:APN, author = "Ioannis Caragiannis and Angelo Fanelli and Nick Gravin and Alexander Skopalik", title = "Approximate Pure {Nash} Equilibria in Weighted Congestion Games: Existence, Efficient Computation, and Structure", journal = j-TEAC, volume = "3", number = "1", pages = "2:1--2:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2614687", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 27 17:58:56 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider structural and algorithmic questions related to the Nash dynamics of weighted congestion games. In weighted congestion games with linear latency functions, the existence of pure Nash equilibria is guaranteed by a potential function argument. Unfortunately, this proof of existence is inefficient and computing pure Nash equilibria in such games is a PLS-hard problem even when all players have unit weights. The situation gets worse when superlinear (e.g., quadratic) latency functions come into play; in this case, the Nash dynamics of the game may contain cycles and pure Nash equilibria may not even exist. Given these obstacles, we consider approximate pure Nash equilibria as alternative solution concepts. A $ \rho $-approximate pure Nash equilibrium is a state of a (weighted congestion) game from which no player has any incentive to deviate in order to improve her cost by a multiplicative factor higher than $ \rho $. Do such equilibria exist for small values of $ \rho $ ? And if so, can we compute them efficiently? We provide positive answers to both questions for weighted congestion games with polynomial latency functions by exploiting an ``approximation'' of such games by a new class of potential games that we call $ \Psi $-games. This allows us to show that these games have $ d!$-approximate pure Nash equilibria, where $d$ is the maximum degree of the latency functions. Our main technical contribution is an efficient algorithm for computing O(1)-approximate pure Nash equilibria when $d$ is a constant. For games with linear latency functions, the approximation guarantee is $ 3 + \sqrt 5 / 2 + O(\gamma)$ for arbitrarily small $ \gamma > 0$; for latency functions with maximum degree $ d \geq 2$, it is $ d 2 d + o (d)$. The running time is polynomial in the number of bits in the representation of the game and $ 1 / \gamma $. As a byproduct of our techniques, we also show the following interesting structural statement for weighted congestion games with polynomial latency functions of maximum degree $ d \geq 2 $: polynomially-long sequences of best-response moves from any initial state to a $ d O (d 2)$-approximate pure Nash equilibrium exist and can be efficiently identified in such games as long as $d$ is a constant. To the best of our knowledge, these are the first positive algorithmic results for approximate pure Nash equilibria in weighted congestion games. Our techniques significantly extend our recent work on unweighted congestion games through the use of $ \Psi $-games. The concept of approximating nonpotential games by potential ones is interesting in itself and might have further applications.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Parkes:2015:BDR, author = "David C. Parkes and Ariel D. Procaccia and Nisarg Shah", title = "Beyond Dominant Resource Fairness: Extensions, Limitations, and Indivisibilities", journal = j-TEAC, volume = "3", number = "1", pages = "3:1--3:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2739040", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 27 17:58:56 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study the problem of allocating multiple resources to agents with heterogeneous demands. Technological advances such as cloud computing and data centers provide a new impetus for investigating this problem under the assumption that agents demand the resources in fixed proportions, known in economics as Leontief preferences. In a recent paper, Ghodsi et al. [2011] introduced the dominant resource fairness (DRF) mechanism, which was shown to possess highly desirable theoretical properties under Leontief preferences. We extend their results in three directions. First, we show that DRF generalizes to more expressive settings, and leverage a new technical framework to formally extend its guarantees. Second, we study the relation between social welfare and properties such as truthfulness; DRF performs poorly in terms of social welfare, but we show that this is an unavoidable shortcoming that is shared by every mechanism that satisfies one of three basic properties. Third, and most importantly, we study a realistic setting that involves indivisibilities. We chart the boundaries of the possible in this setting, contributing a new relaxed notion of fairness and providing both possibility and impossibility results.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Babaioff:2015:DPL, author = "Moshe Babaioff and Shaddin Dughmi and Robert Kleinberg and Aleksandrs Slivkins", title = "Dynamic Pricing with Limited Supply", journal = j-TEAC, volume = "3", number = "1", pages = "4:1--4:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2559152", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 27 17:58:56 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider the problem of designing revenue-maximizing online posted-price mechanisms when the seller has limited supply. A seller has k identical items for sale and is facing n potential buyers (``agents'') that are arriving sequentially. Each agent is interested in buying one item. Each agent's value for an item is an independent sample from some fixed (but unknown) distribution with support [0,1]. The seller offers a take-it-or-leave-it price to each arriving agent (possibly different for different agents), and aims to maximize his expected revenue. We focus on mechanisms that do not use any information about the distribution; such mechanisms are called detail-free (or prior-independent). They are desirable because knowing the distribution is unrealistic in many practical scenarios. We study how the revenue of such mechanisms compares to the revenue of the optimal offline mechanism that knows the distribution (``offline benchmark''). We present a detail-free online posted-price mechanism whose revenue is at most $ O((k \log n)2 / 3) $ less than the offline benchmark, for every distribution that is regular. In fact, this guarantee holds without any assumptions if the benchmark is relaxed to fixed-price mechanisms. Further, we prove a matching lower bound. The performance guarantee for the same mechanism can be improved to $ O (\sqrt k \log n) $, with a distribution-dependent constant, if the ratio $ k / n $ is sufficiently small. We show that, in the worst case over all demand distributions, this is essentially the best rate that can be obtained with a distribution-specific constant. On a technical level, we exploit the connection to multiarmed bandits (MAB). While dynamic pricing with unlimited supply can easily be seen as an MAB problem, the intuition behind MAB approaches breaks when applied to the setting with limited supply. Our high-level conceptual contribution is that even the limited supply setting can be fruitfully treated as a bandit problem.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Dutting:2015:PRT, author = "Paul D{\"u}tting and Felix Fischer and Pichayut Jirapinyo and John K. Lai and Benjamin Lubin and David C. Parkes", title = "Payment Rules through Discriminant-Based Classifiers", journal = j-TEAC, volume = "3", number = "1", pages = "5:1--5:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2559049", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 27 17:58:56 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "In mechanism design it is typical to impose incentive compatibility and then derive an optimal mechanism subject to this constraint. By replacing the incentive compatibility requirement with the goal of minimizing expected ex post regret, we are able to adapt statistical machine learning techniques to the design of payment rules. This computational approach to mechanism design is applicable to domains with multi-dimensional types and situations where computational efficiency is a concern. Specifically, given an outcome rule and access to a type distribution, we train a support vector machine with a specific structure imposed on the discriminant function, such that it implicitly learns a corresponding payment rule with desirable incentive properties. We extend the framework to adopt succinct $k$-wise dependent valuations, leveraging a connection with maximum a posteriori assignment on Markov networks to enable training to scale up to settings with a large number of items; we evaluate this construction in the case where $ k = 2 $. We present applications to multiparameter combinatorial auctions with approximate winner determination, and the assignment problem with an egalitarian outcome rule. Experimental results demonstrate that the construction produces payment rules with low ex post regret, and that penalizing classification error is effective in preventing failures of ex post individual rationality.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Roughgarden:2015:PAG, author = "Tim Roughgarden", title = "The Price of Anarchy in Games of Incomplete Information", journal = j-TEAC, volume = "3", number = "1", pages = "6:1--6:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2737816", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Mar 27 17:58:56 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We define smooth games of incomplete information. We prove an ``extension theorem'' for such games: price of anarchy bounds for pure Nash equilibria for all induced full-information games extend automatically, without quantitative degradation, to all mixed-strategy Bayes--Nash equilibria with respect to a product prior distribution over players' preferences. We also note that, for Bayes--Nash equilibria in games with correlated player preferences, there is no general extension theorem for smooth games. We give several applications of our definition and extension theorem. First, we show that many games of incomplete information for which the price of anarchy has been studied are smooth in our sense. Our extension theorem unifies much of the known work on the price of anarchy in games of incomplete information. Second, we use our extension theorem to prove new bounds on the price of anarchy of Bayes--Nash equilibria in routing games with incomplete information.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Goldstein:2015:IET, author = "Daniel G. Goldstein and R. Preston McAfee and Siddharth Suri", title = "Improving the Effectiveness of Time-Based Display Advertising", journal = j-TEAC, volume = "3", number = "2", pages = "7:1--7:??", month = apr, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2716323", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Apr 21 11:23:36 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Display advertisements are typically sold by the impression, where one impression is simply one download of an ad. Previous work has shown that the longer an ad is in view, the more likely a user is to remember it and that there are diminishing returns to increased exposure time [Goldstein et al. 2011]. Since a pricing scheme that is at least partially based on time is more exact than one based solely on impressions, time-based advertising may become an industry standard. We answer an open question concerning time-based pricing schemes: how should time slots for advertisements be divided? We provide evidence that ads can be scheduled in a way that leads to greater total recollection, which advertisers value, and increased revenue, which publishers value. We document two main findings. First, we show that displaying two shorter ads results in more total recollection than displaying one longer ad of twice the duration. Second, we show that this effect disappears as the duration of these ads increases. We conclude with a theoretical prediction regarding the circumstances under which the display advertising industry would benefit if it moved to a partially or fully time-based standard.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Ganzfried:2015:SOE, author = "Sam Ganzfried and Tuomas Sandholm", title = "Safe Opponent Exploitation", journal = j-TEAC, volume = "3", number = "2", pages = "8:1--8:??", month = apr, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2716322", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Apr 21 11:23:36 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider the problem of playing a repeated two-player zero-sum game safety: that is, guaranteeing at least the value of the game per period in expectation regardless of the strategy used by the opponent. Playing a stage-game equilibrium strategy at each time step clearly guarantees safety, and prior work has (incorrectly) stated that it is impossible to simultaneously deviate from a stage-game equilibrium (in hope of exploiting a suboptimal opponent) and to guarantee safety. We show that such profitable deviations are indeed possible specifically in games where certain types of ``gift'' strategies exist, which we define formally. We show that the set of strategies constituting such gifts can be strictly larger than the set of iteratively weakly-dominated strategies; this disproves another recent assertion which states that all noniteratively weakly dominated strategies are best responses to each equilibrium strategy of the other player. We present a full characterization of safe strategies, and develop efficient algorithms for exploiting suboptimal opponents while guaranteeing safety. We also provide analogous results for extensive-form games of perfect and imperfect information, and present safe exploitation algorithms and full characterizations of safe strategies for those settings as well. We present experimental results in Kuhn poker, a canonical test problem for game-theoretic algorithms. Our experiments show that (1) aggressive safe exploitation strategies significantly outperform adjusting the exploitation within stage-game equilibrium strategies only and (2) all the safe exploitation strategies significantly outperform a (nonsafe) best response strategy against strong dynamic opponents.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Hoefer:2015:SSA, author = "Martin Hoefer and Thomas Kesselheim", title = "Secondary Spectrum Auctions for Symmetric and Submodular Bidders", journal = j-TEAC, volume = "3", number = "2", pages = "9:1--9:??", month = apr, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2739041", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Apr 21 11:23:36 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study truthful auctions for secondary spectrum usage in wireless networks. In this scenario, $n$ communication requests need to be allocated to $k$ available channels that are subject to interference and noise. We present the first truthful mechanisms for secondary spectrum auctions with symmetric or submodular valuations. Our approach to model interference uses an edge-weighted conflict graph, and our algorithms provide asymptotically almost optimal approximation bounds for conflict graphs with a small inductive independence number $ \rho \ll n $. This approach covers a large variety of interference models such as, for instance, the protocol model or the recently popular physical model of interference. For unweighted conflict graphs and symmetric valuations we use LP-rounding to obtain $ O(\rho)$-approximate mechanisms; for weighted conflict graphs we get a factor of $ O(\rho \cdot (\log n + \log k))$. For submodular users we combine the convex rounding framework of Dughmi et al. [2011] with randomized metarounding to obtain $ O(\rho)$-approximate mechanisms for matroid-rank-sum valuations; for weighted conflict graphs we can fully drop the dependence on $k$ to get $ O(\rho \cdot \log n)$. We conclude with promising initial results for deterministically truthful mechanisms that allow approximation factors based on $ \rho $.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Wilkens:2015:SCM, author = "Christopher A. Wilkens and Balasubramanian Sivan", title = "Single-Call Mechanisms", journal = j-TEAC, volume = "3", number = "2", pages = "10:1--10:??", month = apr, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2741027", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Apr 21 11:23:36 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Truthfulness is fragile and demanding. It is oftentimes harder to guarantee truthfulness when solving a problem than it is to solve the problem itself. Even worse, truthfulness can be utterly destroyed by small uncertainties in a mechanism's outcome. One obstacle is that truthful payments depend on outcomes other than the one realized, such as the lengths of non-shortest-paths in a shortest-path auction. Single-call mechanisms are a powerful tool that circumvents this obstacle: they implicitly charge truthful payments, guaranteeing truthfulness in expectation using only the outcome realized by the mechanism. The cost of such truthfulness is a trade-off between the expected quality of the outcome and the risk of large payments. We study two of the most general domains for truthful mechanisms and largely settle when and to what extent single-call mechanisms are possible. The first single-call construction was discovered by Babaioff et al. [2010] in single-parameter domains. They give a transformation that turns any monotone, single-parameter allocation rule into a truthful-in-expectation single-call mechanism. Our first result is a natural complement to Babaioff et al. [2010]: we give a new transformation that produces a single-call VCG mechanism from any allocation rule for which VCG payments are truthful. Second, in both the single-parameter and VCG settings, we precisely characterize the possible transformations, showing that a wide variety of transformations are possible but that all take a very simple form. Finally, we study the inherent trade-off between the expected quality of the outcome and the risk of large payments. We show that our construction and that of Babaioff et al. [2010] simultaneously optimize a variety of metrics in their respective domains. Our study is motivated by settings where uncertainty in a mechanism renders other known techniques untruthful, and we offer a variety of examples where such uncertainty can arise. In particular, we analyze pay-per-click advertising auctions, where the truthfulness of the standard VCG-based auction is easily broken when the auctioneer's estimated click-through-rates are imprecise.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Chakrabarti:2015:TSO, author = "Deepayan Chakrabarti and Erik Vee", title = "Traffic Shaping to Optimize Ad Delivery", journal = j-TEAC, volume = "3", number = "2", pages = "11:1--11:??", month = apr, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2739010", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Apr 21 11:23:36 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Web publishers must balance two objectives: how to keep users engaged by directing them to relevant content, and how to properly monetize this user traffic. The standard approach is to solve each problem in isolation, for example, by displaying content that is tailored to the user's interests so as to maximize clickthrough rates (CTR), and also by building a standalone ad serving system that displays ads depending on the user's characteristics, the article being viewed by the user, and advertiser-specified constraints. However, showing the user only those articles with highest expected CTR precludes the display of some ads; if the publisher had previously guaranteed the delivery of a certain volume of impressions to such ads, then underdelivery penalties might have to be paid. We propose a joint optimization of article selection and ad serving that minimizes underdelivery by shaping some of the incoming traffic to pages where underperforming ads can be displayed, while incurring only minor drops in CTR. In addition to formulating the problem, we design an online optimization algorithm that can find the optimal traffic shaping probabilities for each new user using only a cache of one number per ad contract. Experiments on a large real-world ad-serving Web portal demonstrate significant advantages over the standalone approach: a threefold reduction in underdelivery with only 10\% drop in CTR, or a 2.6-fold reduction with a 4\% CTR drop, and similar results over a wide range.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Ghosh:2015:MME, author = "Arpita Ghosh and Mohammad Mahdian and R. Preston McAfee and Sergei Vassilvitskii", title = "To Match or Not to Match: Economics of Cookie Matching in Online Advertising", journal = j-TEAC, volume = "3", number = "2", pages = "12:1--12:??", month = apr, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2745801", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Tue Apr 21 11:23:36 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Modern online advertising increasingly relies on the ability to follow the same user across the Internet using technology called cookie matching to increase efficiency in ad allocation. Web publishers today use this technology to share information about the websites a user has visited, making it possible to target advertisements to users based on their prior history. This begs the question: do publishers (who are competitors for advertising money) always have the incentive to share online information? Intuitive arguments as well as anecdotal evidence suggest that sometimes a premium publisher might suffer information sharing through an effect called information leakage: by sharing user information with the advertiser, the advertiser will be able to target the same user elsewhere on cheaper publishers, leading to a dilution of the value of the supply on the premium publishers. The goal of this article is to explore this aspect of online information sharing. We show that, when advertisers are homogeneous in the sense that their relative valuations of users are consistent, publishers always agree about the benefits of cookie matching in equilibrium: either all publishers' revenues benefit, or all suffer, from cookie matching. We also show using a simple model that, when advertisers are not homogeneous, the information leakage indeed can occur, with cookie matching helping one publisher's revenues while harming the other.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Kash:2015:EAS, author = "Ian A. Kash and Eric J. Friedman and Joseph Y. Halpern", title = "An Equilibrium Analysis of Scrip Systems", journal = j-TEAC, volume = "3", number = "3", pages = "13:1--13:??", month = jun, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2659006", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:16 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "A game-theoretic model of scrip (artificial currency) systems is analyzed. It is shown that relative entropy can be used to characterize the distribution of agent wealth when all agents use threshold strategies -that is, they volunteer to do work if and only if they have below a threshold amount of money. Monotonicity of agents' best-reply functions is used to show that scrip systems have pure strategy equilibria where all agents use threshold strategies. An algorithm is given that can compute such an equilibrium and the resulting distribution of wealth.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Immorlica:2015:ILR, author = "Nicole Immorlica and Mohammad Mahdian", title = "Incentives in Large Random Two-Sided Markets", journal = j-TEAC, volume = "3", number = "3", pages = "14:1--14:??", month = jun, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2656202", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:16 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Many centralized two-sided markets form a matching between participants by running a stable matching algorithm. It is a well-known fact that no matching mechanism based on a stable matching algorithm can guarantee truthfulness as a dominant strategy for participants. However, we show that in a probabilistic setting where the preference lists on one side of the market are composed of only a constant (independent of the size of the market) number of entries, each drawn from an arbitrary distribution, the number of participants that have more than one stable partner is vanishingly small. This proves (and generalizes) a conjecture of Roth and Peranson [1999]. As a corollary of this result, we show that, with high probability, the truthful strategy is the best response for a random player when the other players are truthful. We also analyze equilibria of the deferred acceptance stable matching game. We show that the game with complete information has an equilibrium in which, in expectation, a $ (1 - o(1)) $ fraction of the strategies are truthful. In the more realistic setting of a game of incomplete information, we will show that the set of truthful strategies form a $ (1 + o(1))$-approximate Bayesian--Nash equilibrium for uniformly random preferences. Our results have implications in many practical settings and are inspired by the work of Roth and Peranson [1999] on the National Residency Matching Program.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Cavallo:2015:DAA, author = "Ruggiero Cavallo and R. Preston Mcafee and Sergei Vassilvitskii", title = "Display Advertising Auctions with Arbitrage", journal = j-TEAC, volume = "3", number = "3", pages = "15:1--15:??", month = jun, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2668033", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:16 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Online display advertising exchanges connect Web publishers with advertisers seeking to place ads. In many cases, the advertiser obtains value from an ad impression (a viewing by a user) only if it is clicked, and frequently advertisers prefer to pay contingent on this occurring. But at the same time, many publishers demand payment independent of clicks. Arbitragers with good estimates of click-probabilities can resolve this conflict by absorbing the risk and acting as an intermediary, paying the publisher on allocation and being paid only if a click occurs. This article examines the incentives of advertisers and arbitragers and contributes an efficient mechanism with truthful bidding by the advertisers and truthful reporting of click predictions by arbitragers as dominant strategies while, given that a hazard rate condition is satisfied, yielding increased revenue to the publisher. We provide empirical evidence based on bid data from Yahoo's Right Media Exchange suggesting that the mechanism would increase revenue in practice.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Bilo:2015:BDN, author = "Davide Bil{\`o} and Luciano Gual{\`a} and Guido Proietti", title = "Bounded-Distance Network Creation Games", journal = j-TEAC, volume = "3", number = "3", pages = "16:1--16:??", month = jun, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2770639", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:16 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "A network creation game simulates a decentralized and noncooperative construction of a communication network. Informally, there are $n$ players sitting on the network nodes, which attempt to establish a reciprocal communication by activating, thereby incurring a certain cost, any of their incident links. The goal of each player is to have all the other nodes as close as possible in the resulting network, while buying as few links as possible. According to this intuition, any model of the game must then appropriately address a balance between these two conflicting objectives. Motivated by the fact that a player might have a strong requirement about her centrality in the network, we introduce a new setting in which a player who maintains her (maximum or average) distance to the other nodes within a given bound incurs a cost equal to the number of activated edges; otherwise her cost is unbounded. We study the problem of understanding the structure of pure Nash equilibria of the resulting games, which we call MaxBD and SumBD, respectively. For both games, we show that when distance bounds associated with players are nonuniform, then equilibria can be arbitrarily bad. On the other hand, for MaxBD, we show that when nodes have a uniform bound $ D \geq 3$ on the maximum distance, then the price of anarchy (PoA) is lower and upper bounded by 2 and $ O(n^{1 / \lfloor \log 3 D \rfloor + 1})$, respectively (i.e., PoA is constant as soon as $D$ is $ \Omega (n^\epsilon)$, for any $ \epsilon > 0$), while for the interesting case $ D = 2$, we are able to prove that the PoA is $ \Omega (\sqrt {n})$ and $ O(\sqrt {n \log n})$. For the uniform SumBD, we obtain similar (asymptotically) results and moreover show that PoA becomes constant as soon as the bound on the average distance is $ 2^{ \omega (\sqrt {\log n})}$.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Chen:2015:ISI, author = "Yiling Chen and Nicole Immorlica", title = "Introduction to the Special Issue on {WINE'13}", journal = j-TEAC, volume = "3", number = "4", pages = "17:1--17:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2796538", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Bateni:2015:RMN, author = "Mohammadhossein Bateni and Nima Haghpanah and Balasubramanian Sivan and Morteza Zadimoghaddam", title = "Revenue Maximization with Nonexcludable Goods", journal = j-TEAC, volume = "3", number = "4", pages = "18:1--18:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2790131", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study the design of revenue-maximizing mechanisms for selling nonexcludable public goods. In particular, we study revenue-maximizing mechanisms in Bayesian settings for facility location problems on graphs where no agent can be excluded from using a facility that has been constructed. We show that the pointwise optimization problem involved in implementing the revenue optimal mechanism, namely, optimizing over arbitrary profiles of virtual values, is hard to approximate within a factor of $ \Omega (n^{2 - \epsilon }) $ (assuming P $ \neq $ NP) even in star graphs. Furthermore, we show that optimizing the expected revenue is APX-hard. However, in a relevant special case, rooted version with identical distributions, we construct polynomial time truthful mechanisms that approximate the optimal expected revenue within a constant factor. We also study the effect of partially mitigating nonexcludability by collecting tolls for using the facilities. We show that such ``posted-price'' mechanisms obtain significantly higher revenue and often approach the optimal revenue obtainable with full excludability.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Minooei:2015:NOR, author = "Hadi Minooei and Chaitanya Swamy", title = "Near-Optimal and Robust Mechanism Design for Covering Problems with Correlated Players", journal = j-TEAC, volume = "3", number = "4", pages = "19:1--19:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2790133", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider the problem of designing incentive-compatible, ex-post individually rational (IR) mechanisms for covering problems in the Bayesian setting, where players' types are drawn from an underlying distribution and may be correlated, and the goal is to minimize the expected total payment made by the mechanism. We formulate a notion of incentive compatibility (IC) that we call support-based IC that is substantially more robust than Bayesian IC, and develop black-box reductions from support-based-IC mechanism design to algorithm design. For single-dimensional settings, this black-box reduction applies even when we only have an LP-relative approximation algorithm for the algorithmic problem. Thus, we obtain near-optimal mechanisms for various covering settings, including single-dimensional covering problems, multi-item procurement auctions, and multidimensional facility location.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Fotakis:2015:TFD, author = "Dimitris Fotakis and Emmanouil Zampetakis", title = "Truthfulness Flooded Domains and the Power of Verification for Mechanism Design", journal = j-TEAC, volume = "3", number = "4", pages = "20:1--20:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2790086", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "In this work, we investigate the reasons that make symmetric partial verification essentially useless in virtually all domains. Departing from previous work, we consider any possible (finite or infinite) domain and general symmetric verification. We identify a natural property, namely, that the correspondence graph of a symmetric verification $M$ is strongly connected by finite paths along which the preferences are consistent with the preferences at the endpoints, and prove that this property is sufficient for the equivalence of truthfulness and $M$-truthfulness. In fact, defining appropriate versions of this property, we obtain this result for deterministic and randomized mechanisms with and without money. Moreover, we show that a slightly relaxed version of this property is also necessary for the equivalence of truthfulness and $M$-truthfulness. Our conditions provide a generic and convenient way of checking whether truthful implementation can take advantage of any symmetric verification scheme in any (finite or infinite) domain. Since the simplest symmetric verification is the local verification, specific cases of our result are closely related, in the case without money, to the research about the equivalence of local truthfulness and global truthfulness. To complete the picture, we consider asymmetric verification and prove that a social choice function is $M$-truthfully implementable by some asymmetric verification $M$ if and only if $f$ does not admit a cycle of profitable deviations.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Kollias:2015:RPE, author = "Konstantinos Kollias and Tim Roughgarden", title = "Restoring Pure Equilibria to Weighted Congestion Games", journal = j-TEAC, volume = "3", number = "4", pages = "21:1--21:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2781678", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Congestion games model several interesting applications, including routing and network formation games, and also possess attractive theoretical properties, including the existence of and convergence of natural dynamics to a pure Nash equilibrium. Weighted variants of congestion games that rely on sharing costs proportional to players' weights do not generally have pure-strategy Nash equilibria. We propose a new way of assigning costs to players with weights in congestion games that recovers the important properties of the unweighted model. This method is derived from the Shapley value, and it always induces a game with a (weighted) potential function. For the special cases of weighted network cost-sharing and weighted routing games with Shapley value-based cost shares, we prove tight bounds on the worst-case inefficiency of equilibria. For weighted network cost-sharing games, we precisely calculate the price of stability for any given player weight vector, while for weighted routing games, we precisely calculate the price of anarchy, as a parameter of the set of allowable cost functions.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Babichenko:2015:QCC, author = "Yakov Babichenko and Siddharth Barman", title = "Query Complexity of Correlated Equilibrium", journal = j-TEAC, volume = "3", number = "4", pages = "22:1--22:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2785668", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study lower bounds on the query complexity of determining correlated equilibrium. In particular, we consider a query model in which an $n$-player game is specified via a black box that returns players' utilities at pure action profiles. In this model, we establish that in order to compute a correlated equilibrium, any deterministic algorithm must query the black box an exponential (in $n$) number of times.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Aumann:2015:EFD, author = "Yonatan Aumann and Yair Dombb", title = "The Efficiency of Fair Division with Connected Pieces", journal = j-TEAC, volume = "3", number = "4", pages = "23:1--23:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2781776", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "The cake-cutting setting, in which a single heterogeneous good must be divided between multiple parties with different tastes, is a classic model for studying questions regarding fairness in resource allocation. In this work, we turn our attention to (economic) efficiency considerations in cake cutting, examining the possible trade-offs between meeting the fairness criteria, on the one hand, and maximizing social welfare, on the other. We focus on divisions that give each agent a single (contiguous) piece of the cake and provide tight bounds (or, in some cases, nearly tight) on the possible degradation in utilitarian and egalitarian welfare resulting from meeting the fairness requirements.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Dimitrov:2015:SPM, author = "Stanko Dimitrov and Rahul Sami and Marina A. Epelman", title = "Subsidized Prediction Mechanisms for Risk-Averse Agents", journal = j-TEAC, volume = "3", number = "4", pages = "24:1--24:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2716327", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "In this article, we study the design and characterization of sequential prediction mechanisms in the presence of agents with unknown risk aversion. We formulate a collection of desirable properties for any sequential forecasting mechanism. We present a randomized mechanism that satisfies all of these properties, including a guarantee that it is myopically optimal for each agent to report honestly, regardless of her degree of risk aversion. We observe, however, that the mechanism has an undesirable side effect: each agent's expected reward, normalized against the inherent value of her private information, decreases exponentially with the number of agents. We prove a negative result showing that this is unavoidable: any mechanism that is myopically strategyproof for agents of all risk types, while also satisfying other natural properties of sequential forecasting mechanisms, must sometimes result in a player getting an exponentially small expected normalized reward.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Xiao:2015:SOD, author = "Yuanzhang Xiao and Mihaela {Van Der Schaar}", title = "Socially-Optimal Design of Service Exchange Platforms with Imperfect Monitoring", journal = j-TEAC, volume = "3", number = "4", pages = "25:1--25:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2785627", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study the design of service exchange platforms in which long-lived anonymous users exchange services with each other. The users are randomly and repeatedly matched into pairs of clients and servers, and each server can choose to provide high-quality or low-quality services to the client with whom it is matched. Since the users are anonymous and incur high costs (e.g., exert high effort) in providing high-quality services, it is crucial that the platform incentivizes users to provide high-quality services. Rating mechanisms have been shown to work effectively as incentive schemes in such platforms. A rating mechanism labels each user by a rating, which summarizes the user's past behaviors, recommends a desirable behavior to each server (e.g., provide higher-quality services for clients with higher ratings), and updates each server's rating based on the recommendation and its client's report on the service quality. Based on this recommendation, a low-rating user is less likely to obtain high-quality services, thereby providing users with incentives to obtain high ratings by providing high-quality services. However, if monitoring or reporting is imperfect-clients do not perfectly assess the quality or the reports are lost-a user's rating may not be updated correctly. In the presence of such errors, existing rating mechanisms cannot achieve the social optimum. In this article, we propose the first rating mechanism that does achieve the social optimum, even in the presence of monitoring or reporting errors. On one hand, the socially-optimal rating mechanism needs to be complicated enough, because the optimal recommended behavior depends not only on the current rating distribution, but also (necessarily) on the history of past rating distributions in the platform. On the other hand, we prove that the social optimum can be achieved by ``simple'' rating mechanisms that use binary rating labels and a small set of (three) recommended behaviors. We provide design guidelines of socially-optimal rating mechanisms and a low-complexity online algorithm for the rating mechanism to determine the optimal recommended behavior.", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Nath:2015:AMD, author = "Swaprava Nath and Arunava Sen", title = "Affine Maximizers in Domains with Selfish Valuations", journal = j-TEAC, volume = "3", number = "4", pages = "26:1--26:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2786014", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Fri Jul 31 19:26:18 MDT 2015", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider the domain of selfish and continuous preferences over a ``rich'' allocation space and show that onto, strategyproof and allocation non-bossy social choice functions are affine maximizers. Roberts [1979] proves this result for a finite set of alternatives and an unrestricted valuation space. In this article, we show that in a subdomain of the unrestricted valuations with the additional assumption of allocation non-bossiness, using the richness of the allocations, the strategyproof social choice functions can be shown to be affine maximizers. We provide an example to show that allocation non-bossiness is indeed critical for this result. This work shows that an affine maximizer result needs a certain amount of richness split across valuations and allocations.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Dutting:2015:EMA, author = "Paul D{\"u}tting and Monika Henzinger and Ingmar Weber", title = "An Expressive Mechanism for Auctions on the {Web}", journal = j-TEAC, volume = "4", number = "1", pages = "1:1--1:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2716312", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:19 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Auctions are widely used on the Web. Applications range from sponsored search to platforms such as eBay. In these and in many other applications the auctions in use are single-/multi-item auctions with unit demand. The main drawback of standard mechanisms for this type of auctions, such as VCG and GSP, is the limited expressiveness that they offer to the bidders. The General Auction Mechanism (GAM) of Aggarwal et al. [2009] takes a first step toward addressing the problem of limited expressiveness by computing a bidder optimal, envy-free outcome for linear utility functions with identical slopes and a single discontinuity per bidder-item pair. We show that in many practical situations this does not suffice to adequately model the preferences of the bidders, and we overcome this problem by presenting the first mechanism for piecewise linear utility functions with nonidentical slopes and multiple discontinuities. Our mechanism runs in polynomial time. Like GAM it is incentive compatible for inputs that fulfill a certain nondegeneracy assumption, but our requirement is more general than the requirement of GAM. For discontinuous utility functions that are nondegenerate as well as for continuous utility functions the outcome of our mechanism is a competitive equilibrium. We also show how our mechanism can be used to compute approximately bidder optimal, envy-free outcomes for a general class of continuous utility functions via piecewise linear approximation. Finally, we prove hardness results for even more expressive settings.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Colini-Baldeschi:2015:MKS, author = "Riccardo Colini-Baldeschi and Stefano Leonardi and Monika Henzinger and Martin Starnberger", title = "On Multiple Keyword Sponsored Search Auctions with Budgets", journal = j-TEAC, volume = "4", number = "1", pages = "2:1--2:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2818357", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:19 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study multiple keyword sponsored search auctions with budgets. Each keyword has multiple ad slots with a click-through rate. The bidders have additive valuations, which are linear in the click-through rates, and budgets, which are restricting their overall payments. Additionally, the number of slots per keyword assigned to a bidder is bounded. We show the following results: (1) We give the first mechanism for multiple keywords, where click-through rates differ among slots. Our mechanism is incentive compatible in expectation, individually rational in expectation, and Pareto optimal. (2) We study the combinatorial setting, where each bidder is only interested in a subset of the keywords. We give an incentive compatible, individually rational, Pareto-optimal, and deterministic mechanism for identical click-through rates. (3) We give an impossibility result for incentive compatible, individually rational, Pareto-optimal, and deterministic mechanisms for bidders with diminishing marginal valuations.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Aumann:2015:ATT, author = "Yonatan Aumann and Yair Dombb and Avinatan Hassidim", title = "Auctioning Time: Truthful Auctions of Heterogeneous Divisible Goods", journal = j-TEAC, volume = "4", number = "1", pages = "3:1--3:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2833086", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:19 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider the problem of auctioning time --- a one-dimensional continuously-divisible heterogeneous good --- among multiple agents. Applications include auctioning time for using a shared device, auctioning TV commercial slots, and more. Different agents may have different valuations for the different possible intervals; the goal is to maximize the aggregate utility. Agents are self-interested and may misrepresent their true valuation functions if this benefits them. Thus, we seek auctions that are truthful. Considering the case that each agent may obtain a single interval, the challenge is twofold, as we need to determine both where to slice the interval, and who gets what slice. We consider two settings: discrete and continuous. In the discrete setting, we are given a sequence of m indivisible elements ( e$_1$, ..., e$_m$ ), and the auction must allocate each agent a consecutive subsequence of the elements. In the continuous setting, we are given a continuous, infinitely divisible interval, and the auction must allocate each agent a subinterval. The agents' valuations are nonatomic measures on the interval. We show that, for both settings, the associated computational problem is NP-complete even under very restrictive assumptions. Hence, we provide approximation algorithms. For the discrete case, we provide a truthful auctioning mechanism that approximates the optimal welfare to within a log m factor. The mechanism works for arbitrary monotone valuations. For the continuous setting, we provide a truthful auctioning mechanism that approximates the optimal welfare to within an O (log n ) factor (where n is the number of agents). Additionally, we provide a truthful 2-approximation mechanism for the case that all pieces must be of some fixed size.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Dutting:2015:AHI, author = "Paul D{\"u}tting and Monika Henzinger and Martin Starnberger", title = "Auctions for Heterogeneous Items and Budget Limits", journal = j-TEAC, volume = "4", number = "1", pages = "4:1--4:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2818351", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:19 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study individual rational, Pareto-optimal, and incentive compatible mechanisms for auctions with heterogeneous items and budget limits. We consider settings with multiunit demand and additive valuations. For single-dimensional valuations we prove a positive result for randomized mechanisms, and a negative result for deterministic mechanisms. While the positive result allows for private budgets, the negative result is for public budgets. For multidimensional valuations and public budgets we prove an impossibility result that applies to deterministic and randomized mechanisms. Taken together this shows the power of randomization in certain settings with heterogeneous items, but it also shows its limitations.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Alon:2015:HPT, author = "Noga Alon and Robert Bredereck and Jiehua Chen and Stefan Kratsch and Rolf Niedermeier and Gerhard J. Woeginger", title = "How to Put Through Your Agenda in Collective Binary Decisions", journal = j-TEAC, volume = "4", number = "1", pages = "5:1--5:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2837467", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:19 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider the following decision-making scenario: a society of voters has to find an agreement on a set of proposals, and every single proposal is to be accepted or rejected. Each voter supports a certain subset of the proposals-the favorite ballot of this voter-and opposes the remaining ones. He accepts a ballot if he supports more than half of the proposals in this ballot. The task is to decide whether there exists a ballot approving a specified number of selected proposals (agenda) such that all voters (or a strict majority of them) accept this ballot. We show that, on the negative side, both problems are NP-complete, and on the positive side, they are fixed-parameter tractable with respect to the total number of proposals or with respect to the total number of voters. We look into further natural parameters and study their influence on the computational complexity of both problems, thereby providing both tractability and intractability results. Furthermore, we provide tight combinatorial bounds on the worst-case size of an accepted ballot in terms of the number of voters.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Fragiadakis:2015:SMM, author = "Daniel Fragiadakis and Atsushi Iwasaki and Peter Troyan and Suguru Ueda and Makoto Yokoo", title = "Strategyproof Matching with Minimum Quotas", journal = j-TEAC, volume = "4", number = "1", pages = "6:1--6:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2841226", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:19 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study matching markets in which institutions may have minimum and maximum quotas. Minimum quotas are important in many settings, such as hospital residency matching, military cadet matching, and school choice, but current mechanisms are unable to accommodate them, leading to the use of ad hoc solutions. We introduce two new classes of strategyproof mechanisms that allow for minimum quotas as an explicit input and show that our mechanisms improve welfare relative to existing approaches. Because minimum quotas cause a theoretical incompatibility between standard fairness and nonwastefulness properties, we introduce new second-best axioms and show that they are satisfied by our mechanisms. Last, we use simulations to quantify (1) the magnitude of the potential efficiency gains from our mechanisms and (2) how far the resulting assignments are from the first-best definitions of fairness and nonwastefulness. Combining both the theoretical and simulation results, we argue that our mechanisms will improve the performance of matching markets with minimum quota constraints in practice.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Babaioff:2016:MDS, author = "Moshe Babaioff and Moran Feldman and Moshe Tennenholtz", title = "Mechanism Design with Strategic Mediators", journal = j-TEAC, volume = "4", number = "2", pages = "7:1--7:??", month = feb, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2841227", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:20 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider the problem of designing mechanisms that interact with strategic agents through strategic intermediaries (or mediators), and investigate the cost to society due to the mediators' strategic behavior. Selfish agents with private information are each associated with exactly one strategic mediator, and can interact with the mechanism exclusively through that mediator. Each mediator aims to optimize the combined utility of his agents, while the mechanism aims to optimize the combined utility of all agents. We focus on the problem of facility location on a metric induced by a publicly known tree. With nonstrategic mediators, there is a dominant strategy mechanism that is optimal. We show that when both agents and mediators act strategically, there is no dominant strategy mechanism that achieves any approximation. We, thus, slightly relax the incentive constraints, and define the notion of a two-sided incentive compatible mechanism. We show that the 3-competitive deterministic mechanism suggested by Procaccia and Tennenholtz [2013] and Dekel et al. [2010] for lines extends naturally to trees, and is still 3-competitive as well as two-sided incentive compatible. This is essentially the best possible (follows from Dekel et al. [2010] and Procaccia and Tennenholtz [2013]). We then show that by allowing randomization one can construct a 2-competitive randomized mechanism that is two-sided incentive compatible, and this is also essentially tight. This result also reduces a gap left in the work of Procaccia and Tennenholtz [2013] and Lu et al. [2009] for the problem of designing strategy-proof mechanisms for weighted agents with no mediators on a line. We also investigate a generalization of the preceding setting where there are multiple levels of mediators.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Roughgarden:2016:NCS, author = "Tim Roughgarden and Okke Schrijvers", title = "Network Cost-Sharing without Anonymity", journal = j-TEAC, volume = "4", number = "2", pages = "8:1--8:??", month = feb, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2841228", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:20 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider network cost-sharing games with nonanonymous cost functions, where the cost of each edge is a submodular function of its users, and this cost is shared using the Shapley value. Nonanonymous cost functions model asymmetries between the players, which can arise from different bandwidth requirements, durations of use, services needed, and so on. These games can possess multiple Nash equilibria of wildly varying quality. The goal of this article is to identify well-motivated equilibrium refinements that admit good worst-case approximation bounds. Our primary results are tight bounds on the cost of strong Nash equilibria and potential function minimizers in network cost-sharing games with nonanonymous cost functions, parameterized by the set C of allowable submodular cost functions. These two worst-case bounds coincide for every set C, and equal the summability parameter introduced in Roughgarden and Sundararajan [2009] to characterize efficiency loss in a family of cost-sharing mechanisms. Thus, a single parameter simultaneously governs the worst-case inefficiency of network cost-sharing games (in two incomparable senses) and cost-sharing mechanisms. This parameter is always at most the $k$th Harmonic number $H_k \approx \ln k$, where $k$ is the number of players, and is constant for many function classes of interest.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Christodoulou:2016:TBP, author = "George Christodoulou and Annam{\'a}ria Kov{\'a}cs and Alkmini Sgouritsa and Bo Tang", title = "Tight Bounds for the Price of Anarchy of Simultaneous First-Price Auctions", journal = j-TEAC, volume = "4", number = "2", pages = "9:1--9:??", month = feb, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2847520", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:20 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study the price of anarchy (PoA) of simultaneous first-price auctions (FPAs) for buyers with submodular and subadditive valuations. The current best upper bounds for the Bayesian price of anarchy (BPoA) of these auctions are e /( e --- 1) [Syrgkanis and Tardos 2013] and 2 [Feldman et al. 2013], respectively. We provide matching lower bounds for both cases even for the case of full information and for mixed Nash equilibria via an explicit construction. We present an alternative proof of the upper bound of e /( e --- 1) for FPAs with fractionally subadditive valuations that reveals the worst-case price distribution, which is used as a building block for the matching lower bound construction. We generalize our results to a general class of item bidding auctions that we call bid-dependent auctions (including FPAs and all-pay auctions) where the winner is always the highest bidder and each bidder's payment depends only on his own bid. Finally, we apply our techniques to discriminatory price multiunit auctions. We complement the results of de Keijzer et al. [2013] for the case of subadditive valuations by providing a matching lower bound of 2. For the case of submodular valuations, we provide a lower bound of 1.109. For the same class of valuations, we were able to reproduce the upper bound of e /( e --- 1) using our nonsmooth approach.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Christodoulou:2016:PSP, author = "George Christodoulou and Martin Gairing", title = "Price of Stability in Polynomial Congestion Games", journal = j-TEAC, volume = "4", number = "2", pages = "10:1--10:??", month = feb, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2841229", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:20 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "The price of anarchy (PoA) in congestion games has attracted a lot of research over the past decade. This has resulted in a thorough understanding of this concept. In contrast, the price of stability (PoS), which is an equally interesting concept, is much less understood. In this article, we consider congestion games with polynomial cost functions with nonnegative coefficients and maximum degree d. We give matching bounds for the PoS in such games-that is, our technique provides the exact value for any degree d. For linear congestion games, tight bounds were previously known. Those bounds hold even for the more restricted case of dominant equilibria, which may not exist. We give a separation result showing that this is not possible for congestion games with quadratic cost functions-in other words, the PoA for the subclass of games that admit a dominant strategy equilibrium is strictly smaller than the PoS for the general class.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Hoefer:2016:TSD, author = "Martin Hoefer and Thomas Kesselheim and Berthold V{\"o}cking", title = "Truthfulness and Stochastic Dominance with Monetary Transfers", journal = j-TEAC, volume = "4", number = "2", pages = "11:1--11:??", month = feb, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2847522", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Sat Feb 6 08:20:20 MST 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We consider truthfulness concepts for auctions with payments based on first- and second-order stochastic dominance. We assume bidders consider wealth in standard quasilinear form as valuation minus payments. Additionally, they are sensitive to risk in the distribution of wealth stemming from randomized mechanisms. First- and second-order stochastic dominance are well known to capture risk sensitivity, and we apply these concepts to capture truth-telling incentives for bidders. As our first main result, we provide a complete characterization of all social-choice functions over binary single-parameter domains that can be implemented by a mechanism that is truthful in first- and second-order stochastic dominance. We show that these are exactly the social-choice functions implementable by truthful-in-expectation mechanisms, and we provide a novel payment rule that guarantees stochastic dominance. As our second main result we extend the celebrated randomized metarounding approach for truthful-in-expectation mechanisms in packing domains. We design mechanisms that are truthful in first-order stochastic dominance by spending only a logarithmic factor in the approximation guarantee.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Mcafee:2016:I, author = "Preston Mcafee and {\'E}va Tardos", title = "Introduction", journal = j-TEAC, volume = "4", number = "3", pages = "12:1--12:??", month = jun, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2916701", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Thu Jun 16 09:24:17 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Chen:2016:TMA, author = "Yiling Chen and Stephen Chong and Ian A. Kash and Tal Moran and Salil Vadhan", title = "Truthful Mechanisms for Agents That Value Privacy", journal = j-TEAC, volume = "4", number = "3", pages = "13:1--13:??", month = jun, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2892555", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Thu Jun 16 09:24:17 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Recent work has constructed economic mechanisms that are both truthful and differentially private. In these mechanisms, privacy is treated separately from truthfulness; it is not incorporated in players' utility functions (and doing so has been shown to lead to nontruthfulness in some cases). In this work, we propose a new, general way of modeling privacy in players' utility functions. Specifically, we only assume that if an outcome o has the property that any report of player i would have led to o with approximately the same probability, then o has a small privacy cost to player i. We give three mechanisms that are truthful with respect to our modeling of privacy: for an election between two candidates, for a discrete version of the facility location problem, and for a general social choice problem with discrete utilities (via a VCG-like mechanism). As the number n of players increases, the social welfare achieved by our mechanisms approaches optimal (as a fraction of n ).", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Devanur:2016:WPO, author = "Nikhil R. Devanur and Zhiyi Huang and Nitish Korula and Vahab S. Mirrokni and Qiqi Yan", title = "Whole-Page Optimization and Submodular Welfare Maximization with Online Bidders", journal = j-TEAC, volume = "4", number = "3", pages = "14:1--14:??", month = jun, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2892563", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Thu Jun 16 09:24:17 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "In the context of online ad serving, display ads may appear on different types of web pages, where each page includes several ad slots and therefore multiple ads can be shown on each page. The set of ads that can be assigned to ad slots of the same page needs to satisfy various prespecified constraints including exclusion constraints, diversity constraints, and the like. Upon arrival of a user, the ad serving system needs to allocate a set of ads to the current webpage respecting these per-page allocation constraints. Previous slot-based settings ignore the important concept of a page and may lead to highly suboptimal results in general. In this article, motivated by these applications in display advertising and inspired by the submodular welfare maximization problem with online bidders, we study a general class of page-based ad allocation problems, present the first (tight) constant-factor approximation algorithms for these problems, and confirm the performance of our algorithms experimentally on real-world datasets. A key technical ingredient of our results is a novel primal-dual analysis for handling free disposal, which updates dual variables using a ``level function'' instead of a single level and unifies with previous analyses of related problems. This new analysis method allows us to handle arbitrarily complicated allocation constraints for each page. Our main result is an algorithm that achieves a $1 - 1 / e - o(1)$-competitive ratio. Moreover, our experiments on real-world datasets show significant improvements of our page-based algorithms compared to the slot-based algorithms. Finally, we observe that our problem is closely related to the submodular welfare maximization (SWM) problem. In particular, we introduce a variant of the SWM problem with online bidders and show how to solve this problem using our algorithm for whole-page optimization.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Caragiannis:2016:WDN, author = "Ioannis Caragiannis and Ariel D. Procaccia and Nisarg Shah", title = "When Do Noisy Votes Reveal the Truth?", journal = j-TEAC, volume = "4", number = "3", pages = "15:1--15:??", month = jun, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2892565", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Thu Jun 16 09:24:17 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "A well-studied approach to the design of voting rules views them as maximum likelihood estimators; given votes that are seen as noisy estimates of a true ranking of the alternatives, the rule must reconstruct the most likely true ranking. We argue that this is too stringent a requirement and instead ask: how many votes does a voting rule need to reconstruct the true ranking? We define the family of pairwise-majority consistent rules and show that for all rules in this family, the number of samples required from Mallows's noise model is logarithmic in the number of alternatives, and that no rule can do asymptotically better (while some rules like plurality do much worse). Taking a more normative point of view, we consider voting rules that surely return the true ranking as the number of samples tends to infinity (we call this property accuracy in the limit ); this allows us to move to a higher level of abstraction. We study families of noise models that are parameterized by distance functions and find voting rules that are accurate in the limit for all noise models in such general families. We characterize the distance functions that induce noise models for which pairwise-majority consistent rules are accurate in the limit and provide a similar result for another novel family of position-dominance consistent rules. These characterizations capture three well-known distance functions.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Easley:2016:IGG, author = "David Easley and Arpita Ghosh", title = "Incentives, Gamification, and Game Theory: an Economic Approach to Badge Design", journal = j-TEAC, volume = "4", number = "3", pages = "16:1--16:??", month = jun, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2910575", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Thu Jun 16 09:24:17 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Gamification is growing increasingly prevalent as a means to incentivize user engagement of social media sites that rely on user contributions. Badges, or equivalent rewards, such as top-contributor lists that are used to recognize a user's contributions on a site, clearly appear to be valued by users who actively pursue and compete for them. However, different sites use different badge designs, varying how, and for what, badges are awarded. Some sites, such as StackOverflow, award badges for meeting fixed levels of contribution. Other sites, such as Amazon and Y! Answers, reward users for being among some top set of contributors on the site, corresponding to a competitive standard of performance. Given that users value badges, and that contributing to a site requires effort, how badges are designed will affect the incentives-therefore the participation and effort-elicited from strategic users on a site. We take a game-theoretic approach to badge design, analyzing the incentives created by widely used badge designs in a model in which winning a badge is valued, effort is costly, and potential contributors to the site endogenously decide whether or not to participate, and how much total effort to put into their contributions to the site. We analyze equilibrium existence, as well as equilibrium participation and effort, in an absolute standards mechanism $M_\alpha$ in which badges are awarded for meeting some absolute level of (observed) effort, and a relative standards mechanism $M_\rho$ corresponding to competitive standards, as in a top-$\rho$ contributor badge. We find that equilibria always exist in both mechanisms, even when the value from winning a badge depends endogenously on the number of other winners. However, $M_\alpha$ has zero-participation equilibria for standards that are too high, whereas all equilibria in $M_\rho$ elicit nonzero participation for all possible $\rho$, provided that $\rho$ is specified as a fixed number rather than as a fraction of actual contributors (note that the two are not equivalent in a setting with endogenous participation). Finally, we ask whether or not a site should explicitly announce the number of users winning a badge. The answer to this question is determined by the curvature of the value of winning the badge as a function of the number of other winners.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Roberts:2016:RTS, author = "Ben Roberts and Dinan Gunawardena and Ian A. Kash and Peter Key", title = "Ranking and Tradeoffs in Sponsored Search Auctions", journal = j-TEAC, volume = "4", number = "3", pages = "17:1--17:??", month = jun, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2910576", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Thu Jun 16 09:24:17 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "In a sponsored search auction, decisions about how to rank ads impose tradeoffs between objectives, such as revenue and welfare. In this article, we examine how these tradeoffs should be made. We begin by arguing that the most natural solution concept to evaluate these tradeoffs is the lowest symmetric Nash equilibrium (SNE). As part of this argument, we generalise the well-known connection between the lowest SNE and the VCG outcome. We then propose a new ranking algorithm, loosely based on the revenue-optimal auction, that uses a reserve price to order the ads (not just to filter them) and give conditions under which it raises more revenue than simply applying that reserve price. Finally, we conduct extensive simulations examining the tradeoffs enabled by different ranking algorithms and show that our proposed algorithm enables superior operating points by a variety of metrics.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Roughgarden:2016:ORM, author = "Tim Roughgarden and Inbal Talgam-Cohen", title = "Optimal and Robust Mechanism Design with Interdependent Values", journal = j-TEAC, volume = "4", number = "3", pages = "18:1--18:??", month = jun, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2910577", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Thu Jun 16 09:24:17 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study interdependent value settings and extend several results from the well-studied independent private values model to these settings. For revenue-optimal mechanism design, we give conditions under which Myerson's virtual value-based mechanism remains optimal with interdependent values. One of these conditions is robustness of the truthfulness and individual rationality guarantees, in the sense that they are required to hold ex-post. We then consider an even more robust class of mechanisms called ``prior independent'' (``detail free''), and show that, by simply using one of the bidders to set a reserve price, it is possible to extract near-optimal revenue in an interdependent values setting. This shows that a considerable level of robustness is achievable for interdependent values in single-parameter environments.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Conitzer:2016:ISI, author = "Vincent Conitzer and David Easley", title = "Introduction to the Special Issue on {EC'14}", journal = j-TEAC, volume = "4", number = "4", pages = "19:1--19:??", month = aug, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2953046", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Aug 29 06:37:22 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Othman:2016:CFT, author = "Abraham Othman and Christos Papadimitriou and Aviad Rubinstein", title = "The Complexity of Fairness Through Equilibrium", journal = j-TEAC, volume = "4", number = "4", pages = "20:1--20:??", month = aug, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2956583", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Aug 29 06:37:22 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Competitive equilibrium from equal incomes (CEEI) is a well-known fair allocation mechanism with desirable fairness and efficiency properties; however, with indivisible resources, a CEEI may not exist [Foley 1967; Varian 1974; Thomson and Varian 1985]. It was shown in Budish [2011] that in the case of indivisible resources, there is always an allocation, called A-CEEI, that is approximately fair, approximately truthful, and approximately efficient for some favorable approximation parameters. A heuristic search that attempts to find this approximation is used in practice to assign business school students to courses. In this article, we show that finding the A-CEEI allocation guaranteed to exist by Budish's theorem is PPAD-complete. We further show that finding an approximate equilibrium with better approximation guarantees is even harder: NP-complete.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Hassidim:2016:LCM, author = "Avinatan Hassidim and Yishay Mansour and Shai Vardi", title = "Local Computation Mechanism Design", journal = j-TEAC, volume = "4", number = "4", pages = "21:1--21:??", month = aug, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2956584", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Aug 29 06:37:22 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We introduce the notion of local computation mechanism design -designing game-theoretic mechanisms that run in polylogarithmic time and space. Local computation mechanisms reply to each query in polylogarithmic time and space, and the replies to different queries are consistent with the same global feasible solution. When the mechanism employs payments, the computation of the payments is also done in polylogarithmic time and space. Furthermore, the mechanism needs to maintain incentive compatibility with respect to the allocation and payments. We present local computation mechanisms for two classical game-theoretical problems: stable matching and job scheduling. For stable matching, some of our techniques may have implications to the global (non-LCA (Local Computation Algorithm)) setting. Specifically, we show that when the men's preference lists are bounded, we can achieve an arbitrarily good approximation to the stable matching within a fixed number of iterations of the Gale--Shapley algorithm.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Ghosh:2016:OCD, author = "Arpita Ghosh and Robert Kleinberg", title = "Optimal Contest Design for Simple Agents", journal = j-TEAC, volume = "4", number = "4", pages = "22:1--22:??", month = aug, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2930955", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Aug 29 06:37:22 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Incentives are more likely to elicit desired outcomes when they are designed based on accurate models of agents' strategic behavior. A growing literature, however, suggests that people do not quite behave like standard economic agents in a variety of environments, both online and offline. What consequences might such differences have for the optimal design of mechanisms in these environments? In this article, we explore this question in the context of optimal contest design for simple agents-agents who strategically reason about whether or not to participate in a system, but not about the input they provide to it. Specifically, consider a contest where n potential contestants with types $ (q_i, c^i) $ each choose between participating and producing a submission of quality q$^i$ at cost c$^i$, versus not participating at all to maximize their utilities. How should a principal distribute a total prize V among the n ranks to maximize some increasing function of the qualities of elicited submissions in a contest with such simple agents? We first solve the optimal contest design problem for settings where agents have homogeneous participation costs $ c^i = c$. Here, the contest that maximizes every increasing function of the elicited contributions is always a simple contest, awarding equal prizes of $ V / j^*$ each to the top $ j^*= V / c - \Theta (\sqrt { V / (c \ln (V / c))})$ contestants. This is in contrast to the optimal contest structure in comparable models with strategic effort choices, where the optimal contest is either a winner-take-all contest or awards possibly unequal prizes, depending on the curvature of agents' effort cost functions. We next address the general case with heterogeneous costs where agents' types $ (q^i, c^i)$ are inherently two dimensional, significantly complicating equilibrium analysis. With heterogeneous costs, the optimal contest depends on the objective being maximized: our main result here is that the winner-take-all contest is a 3-approximation of the optimal contest when the principal's objective is to maximize the quality of the best elicited contribution. The proof of this result hinges around a ``subequilibrium'' lemma establishing a stochastic dominance relation between the distribution of qualities elicited in an equilibrium and a subequilibrium --- a strategy profile that is a best response for all agents who choose to participate in that strategy profile; this relation between equilibria and subequilibria may be of more general interest.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Fudenberg:2016:RRR, author = "Drew Fudenberg and Alexander Peysakhovich", title = "Recency, Records, and Recaps: Learning and Nonequilibrium Behavior in a Simple Decision Problem", journal = j-TEAC, volume = "4", number = "4", pages = "23:1--23:??", month = aug, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2956581", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Aug 29 06:37:22 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "Nash equilibrium takes optimization as a primitive, but suboptimal behavior can persist in simple stochastic decision problems. This has motivated the development of other equilibrium concepts such as cursed equilibrium and behavioral equilibrium. We experimentally study a simple adverse selection (or ``lemons'') problem and find that learning models that heavily discount past information (i.e., display recency bias) explain patterns of behavior better than Nash, cursed, or behavioral equilibrium. Providing counterfactual information or a record of past outcomes does little to aid convergence to optimal strategies, but providing sample averages (``recaps'') gets individuals most of the way to optimality. Thus, recency effects are not solely due to limited memory but stem from some other form of cognitive constraints. Our results show the importance of going beyond static optimization and incorporating features of human learning into economic models used in both understanding phenomena and designing market institutions.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Goldberg:2016:BQC, author = "Paul W. Goldberg and Aaron Roth", title = "Bounds for the Query Complexity of Approximate Equilibria", journal = j-TEAC, volume = "4", number = "4", pages = "24:1--24:??", month = aug, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2956582", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Aug 29 06:37:22 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We analyze the number of payoff queries needed to compute approximate equilibria of multi-player games. We find that query complexity is an effective tool for distinguishing the computational difficulty of alternative solution concepts, and we develop new techniques for upper- and lower bounding the query complexity. For binary-choice games, we show logarithmic upper and lower bounds on the query complexity of approximate correlated equilibrium. For well-supported approximate correlated equilibrium (a restriction where a player's behavior must always be approximately optimal, in the worst case over draws from the distribution) we show a linear lower bound, thus separating the query complexity of well supported approximate correlated equilibrium from the standard notion of approximate correlated equilibrium. Finally, we give a query-efficient reduction from the problem of computing an approximate well-supported Nash equilibrium to the problem of verifying a well supported Nash equilibrium, where the additional query overhead is proportional to the description length of the game. This gives a polynomial-query algorithm for computing well supported approximate Nash equilibria (and hence correlated equilibria) in concisely represented games. We identify a class of games (which includes congestion games) in which the reduction can be made not only query efficient, but also computationally efficient.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", } @Article{Fearnley:2016:FAN, author = "John Fearnley and Rahul Savani", title = "Finding Approximate {Nash} Equilibria of Bimatrix Games via Payoff Queries", journal = j-TEAC, volume = "4", number = "4", pages = "25:1--25:??", month = aug, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2956579", ISSN = "2167-8375 (print), 2167-8383 (electronic)", ISSN-L = "1539-9087", bibdate = "Mon Aug 29 06:37:22 MDT 2016", bibsource = "http://portal.acm.org/; http://www.math.utah.edu/pub/tex/bib/teac.bib", abstract = "We study the deterministic and randomized query complexity of finding approximate equilibria in a $ k \times k $ bimatrix game. We show that the deterministic query complexity of finding an \epsilon -Nash equilibrium when $ \epsilon < 1 / 2 $ is $ \Omega (k^2) $, even in zero-one constant-sum games. In combination with previous results [Fearnley et al. 2013], this provides a complete characterization of the deterministic query complexity of approximate Nash equilibria. We also study randomized querying algorithms. We give a randomized algorithm for finding a $ (3 - \sqrt {5 / 2 + \epsilon })$-Nash equilibrium using $ O(k \log k / \epsilon^2)$ payoff queries, which shows that the $ 1 / 2$ barrier for deterministic algorithms can be broken by randomization. For well-supported Nash equilibria (WSNE), we first give a randomized algorithm for finding an $ \epsilon $-WSNE of a zero-sum bimatrix game using $ O (k \log k / \epsilon^4)$ payoff queries, and we then use this to obtain a randomized algorithm for finding a $ (2 / 3 + \epsilon)$-WSNE in a general bimatrix game using $ O(k \log k / \epsilon^4)$ payoff queries. Finally, we initiate the study of lower bounds against randomized algorithms in the context of bimatrix games, by showing that randomized algorithms require $ \Omega (k^2)$ payoff queries in order to find an $ \epsilon $-Nash equilibrium with $ \epsilon < 1 / 4 k$, even in zero-one constant-sum games. In particular, this rules out query-efficient randomized algorithms for finding exact Nash equilibria.", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Economics and Computation", journal-URL = "http://dl.acm.org/citation.cfm?id=2542174", }