{"title":"Network Cost-Sharing without Anonymity","authors":"T. Roughgarden, Okke Schrijvers","doi":"10.1145/2841228","DOIUrl":"https://doi.org/10.1145/2841228","url":null,"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.\u0000 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.\u0000 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 kth Harmonic number Hk ≈ ln k, where k is the number of players, and is constant for many function classes of interest.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129993641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Matthew Cary, Aparna Das, Benjamin Edelman, Ioannis Giotis, Kurtis Heimerl, Anna R. Karlin, S. Kominers, Claire Mathieu, M. Schwarz
{"title":"Convergence of Position Auctions under Myopic Best-Response Dynamics","authors":"Matthew Cary, Aparna Das, Benjamin Edelman, Ioannis Giotis, Kurtis Heimerl, Anna R. Karlin, S. Kominers, Claire Mathieu, M. Schwarz","doi":"10.1145/2632226","DOIUrl":"https://doi.org/10.1145/2632226","url":null,"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.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116944570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The Query Complexity of Scoring Rules","authors":"Pablo Azar, S. Micali","doi":"10.1145/2632228","DOIUrl":"https://doi.org/10.1145/2632228","url":null,"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 ω, 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.\u0000 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.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129523769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yiling Chen, Ian A. Kash, Michael Ruberry, V. Shnayder
{"title":"Eliciting Predictions and Recommendations for Decision Making","authors":"Yiling Chen, Ian A. Kash, Michael Ruberry, V. Shnayder","doi":"10.1145/2556271","DOIUrl":"https://doi.org/10.1145/2556271","url":null,"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.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131305161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Rating Protocols in Online Communities","authors":"Yu Zhang, Jaeok Park, M. Schaar","doi":"10.1145/2560794","DOIUrl":"https://doi.org/10.1145/2560794","url":null,"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.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116089169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Signaling Competition and Social Welfare","authors":"Gleb Polevoy, Rann Smorodinsky, Moshe Tennenholtz","doi":"10.1145/2560766","DOIUrl":"https://doi.org/10.1145/2560766","url":null,"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.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130146334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Christodoulou, Annamária Kovács, A. Sgouritsa, Bo Tang
{"title":"Tight Bounds for the Price of Anarchy of Simultaneous First-Price Auctions","authors":"G. Christodoulou, Annamária Kovács, A. Sgouritsa, Bo Tang","doi":"10.1145/2847520","DOIUrl":"https://doi.org/10.1145/2847520","url":null,"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.\u0000 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.\u0000 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.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130671970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. E. Yildiz, A. Ozdaglar, D. Acemoglu, A. Saberi, A. Scaglione
{"title":"Binary Opinion Dynamics with Stubborn Agents","authors":"M. E. Yildiz, A. Ozdaglar, D. Acemoglu, A. Saberi, A. Scaglione","doi":"10.1145/2538508","DOIUrl":"https://doi.org/10.1145/2538508","url":null,"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.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127746799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Competitive Shopbots-Mediated Markets","authors":"David Sarne","doi":"10.1145/2509413.2509417","DOIUrl":"https://doi.org/10.1145/2509413.2509417","url":null,"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.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116416380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Price of Stability in Polynomial Congestion Games","authors":"G. Christodoulou, M. Gairing","doi":"10.1145/2841229","DOIUrl":"https://doi.org/10.1145/2841229","url":null,"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.\u0000 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.\u0000 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.","PeriodicalId":194623,"journal":{"name":"ACM Trans. Economics and Comput.","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124697448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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