Proceedings of the Sixteenth ACM Conference on Economics and Computation最新文献

{"title":"Near Feasible Stable Matchings","authors":"Thành Nguyen, R. Vohra","doi":"10.1145/2764468.2764471","DOIUrl":"https://doi.org/10.1145/2764468.2764471","url":null,"abstract":"The National Resident Matching program strives for a stable matching of medical students to teaching hospitals. With the presence of couples, stable matchings need not exist. For any student preferences, we show that each instance of a stable matching problem has a 'nearby' instance with a stable matching. The nearby instance is obtained by perturbing the capacities of the hospitals. Our approach is general and applies to other type of complementarities, as well as matchings with side constraints and contracts.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121923665","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":"Finding Any Nontrivial Coarse Correlated Equilibrium Is Hard","authors":"Siddharth Barman, Katrina Ligett","doi":"10.1145/2764468.2764497","DOIUrl":"https://doi.org/10.1145/2764468.2764497","url":null,"abstract":"One of the most appealing aspects of the (coarse) correlated equilibrium concept is that natural dynamics quickly arrive at approximations of such equilibria, even in games with many players. In addition, there exist polynomial-time algorithms that compute exact (coarse) correlated equilibria. In light of these results, a natural question is how good are the (coarse) correlated equilibria that can arise from any efficient algorithm or dynamics. In this paper we address this question, and establish strong negative results. In particular, we show that in multiplayer games that have a succinct representation, it is NP-hard to compute any coarse correlated equilibrium (or approximate coarse correlated equilibrium) with welfare strictly better than the worst possible. The focus on succinct games ensures that the underlying complexity question is interesting; many multiplayer games of interest are in fact succinct. Our results imply that, while one can efficiently compute a coarse correlated equilibrium, one cannot provide any nontrivial welfare guarantee for the resulting equilibrium, unless P=NP. We show that analogous hardness results hold for correlated equilibria, and persist under the egalitarian objective or Pareto optimality. To complement the hardness results, we develop an algorithmic framework that identifies settings in which we can efficiently compute an approximate correlated equilibrium with near-optimal welfare. We use this framework to develop an efficient algorithm for computing an approximate correlated equilibrium with near-optimal welfare in aggregative games.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131107063","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":"Matching with Stochastic Arrival","authors":"Neil Thakral","doi":"10.4108/eai.8-8-2015.2260625","DOIUrl":"https://doi.org/10.4108/eai.8-8-2015.2260625","url":null,"abstract":"We study matching in a dynamic setting, with applications to the allocation of public housing. In our model, objects of different types that arrive stochastically over time must be allocated to agents in a queue. For the case that the objects share a common priority ordering over agents, we introduce a strategy-proof mechanism that satisfies certain fairness and efficiency properties. More generally, we show that the mechanism continues to satisfy these properties if and only if the priority relations satisfy an acyclicity condition. We then turn to an application of the framework by evaluating the procedures that are currently being used to allocate public housing. The estimated welfare gains from adopting the new mechanism are substantial, exceeding $5,000 per applicant.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128300592","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":"Smooth Online Mechanisms: A Game-Theoretic Problem in Renewable Energy Markets","authors":"Thomas Kesselheim, Robert D. Kleinberg, É. Tardos","doi":"10.1145/2764468.2764487","DOIUrl":"https://doi.org/10.1145/2764468.2764487","url":null,"abstract":"Using renewable energy in an efficient way is a key challenge facing our society. In this paper we study online mechanisms motivated by markets for such renewable energy, such as wind energy. While the aggregate demand of the large populations served by energy providers is quite predictable, supply in such systems is rather uncertain; e.g. it depends on the strength of the wind at the wind turbines. Energy, when it is available, must be delivered immediately, due to the inefficiency of technologies for electric power storage, hence the supply is perishable. We model this scenario with an online market where supply is unknown, but participants know their own demand, and bid for energy at the beginning of the period. Items arrive online and are perishable, meaning that they have to be allocated to bidders immediately after arrival. This setup have been used for modeling renewable energy markets by earlier works, such as Tan and Varaiya (1993). We perform a price-of-anarchy analysis for a simple greedy allocation scheme, and compare efficiency of equilibria and learning outcomes to the socially optimal offline allocation. Due to the uncertainty, traditional dominant-strategy truthfulness cannot be achieved except by trivial mechanisms, which makes simple allocation mechanisms, such as the greedy, an appealing alternative. We show that simple first-price or second-price auctions combined with a greedy allocation rule ensure that equilibria closely approximate the optimum, assuming that bidders' preferences are non-increasing over time and additive within their demand, and demand is captured by a cardinality or matroid constraint. The results are of interest not only due to the application to energy markets, but also as they provide the first successful bounds on the price of anarchy of mechanisms in any online setting, while for the classical sequential auction setting Paes Leme et al. (2012) show that the price of anarchy is prohibitively high even with very simple bidder utilities. In more detail, we prove that equilibria and learning outcomes ensure at least half of the optimal welfare in case of the first-price rule with cardinality constraints, matching the approximation bound for the greedy algorithm. For second-price and more general matroid constraints, we show weaker guarantees. All results also extend to the Bayesian setting, where player values are random: bidder know their own future demand, but the competition is uncertain as is the supply, and all values may be correlated.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127377971","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":"Online Reputation Management: Estimating the Impact of Management Responses on Consumer Reviews","authors":"Davide Proserpio, G. Zervas","doi":"10.2139/ssrn.2521190","DOIUrl":"https://doi.org/10.2139/ssrn.2521190","url":null,"abstract":"Failure to meet a consumer's expectations can result in a negative review, which can have a lasting, damaging impact on a firm's reputation, and its ability to attract new customers. To mitigate the reputational harm of negative reviews many firms now publicly respond to them. How effective is this reputation management strategy in improving a firm's reputation? We empirically answer this question by exploiting a difference in managerial practice across two hotel review platforms, TripAdvisor and Expedia: while hotels regularly respond to their TripAdvisor reviews, they almost never do so on Expedia. Based on this observation, we use difference-in-differences to identify the causal impact of management responses on consumer ratings by comparing changes in the TripAdvisor ratings of a hotel following its decision to begin responding against a baseline of changes in the same hotel's Expedia ratings. We find that responding hotels, which account for 56% of hotels in our data, see an average increase of 0.12 stars in the TripAdvisor ratings they receive after they start responding. Moreover, we show that this increase in ratings does not arise from hotel quality investments. Instead, we find that the increase is consistent with a shift in reviewer selection: consumers with a poor experience become less likely to leave a negative review when hotels begin responding.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125407995","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":"Short Lists in Centralized Clearinghouses","authors":"N. Arnosti","doi":"10.1145/2764468.2764533","DOIUrl":"https://doi.org/10.1145/2764468.2764533","url":null,"abstract":"Stable matching mechanisms are used to clear many two-sided markets. In most settings, frictions cause participants to submit short preference lists (even if there are many potentially acceptable matches). This paper studies the consequences of this fact, and focuses on two broad questions. First, when lists are short, what is the quantity and quality of matches formed through the clearinghouse? Second, what are the effects of introducing an aftermarket which allows agents left unmatched by the clearinghouse to find one another? The answers to these questions depend crucially on the extent and form of correlations in agent preferences. I consider three canonical preference structures: fully independent (or idiosyncratic) preferences, vertical preferences (agents agree on the attractiveness of those on the opposite side), and aligned preferences (potential partners agree on the attractiveness of their match). I find that when agent preferences are idiosyncratic, more matches form than when agents are vertically differentiated. Perhaps more surprisingly, I show that the case of aligned preferences causes the fewest matches to form. When considering quality of matches, the story reverses itself: aligned preferences produce the most high quality matches, followed by correlated preferences, with independent preferences producing the fewest. These facts have implications for the design of priority structures and tie-breaking procedures in school choice settings, as they point to a fundamental tradeoff between matching many students, and maximizing the number of students who get one of their top choices. Regarding the role of the aftermarket, I find that when preferences are aligned, the aftermarket unambiguously improves the welfare of both sides. In other cases, however, the introduction of an aftermarket has multiple competing effects, and may either raise or lower aggregate welfare. This suggests that when designing an aftermarket, the extent and form of correlations in agent preferences are an important factor to consider.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125121507","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":"Mechanisms for Fair Attribution","authors":"Eric Balkanski, Yaron Singer","doi":"10.1145/2764468.2764505","DOIUrl":"https://doi.org/10.1145/2764468.2764505","url":null,"abstract":"We propose a new framework for optimization under fairness constraints. The problems we consider model procurement where the goal is to optimize a buyer's utility while paying sellers in a manner that reflects their contribution to the buyer's utility. The payment rules we consider are natural interpretations of fairness based on concepts such as Shapley values and the nucleolus from cooperative game theory. The question in this setting is whether the outcome (measured in terms of the buyer's utility) produced by mechanisms that enforce fair payments is competitive with the outcome of a mechanism that simply pays agents their costs and is not committed to fair payments. Our main result shows that there exists a mechanism which guarantees a solution whose value is at least one third of the optimal unfair solution for any submodular utility function, and that this ratio is optimal. We discuss several special cases for which this approximation ratio can be improved and natural extensions.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115697415","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":"Canary in the e-Commerce Coal Mine: Detecting and Predicting Poor Experiences Using Buyer-to-Seller Messages","authors":"Dimitriy V. Masterov, U. Mayer, S. Tadelis","doi":"10.1145/2764468.2764499","DOIUrl":"https://doi.org/10.1145/2764468.2764499","url":null,"abstract":"Reputation and feedback systems in online marketplaces are often biased, making it difficult to ascertain the quality of sellers. We use post-transaction, buyer-to-seller message traffic to detect signals of unsatisfactory transactions on eBay. We posit that a message sent after the item was paid for serves as a reliable indicator that the buyer may be unhappy with that purchase, particularly when the message included words associated with a negative experience. The fraction of a seller's message traffic that was negative predicts whether a buyer who transacts with this seller will stop purchasing on eBay, implying that platforms can use these messages as an additional signal of seller quality.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115288336","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":"Decentralized Dynamics and Fast Convergence in the Assignment Game: Extended Abstract","authors":"Bary S. R. Pradelski","doi":"10.1145/2764468.2764470","DOIUrl":"https://doi.org/10.1145/2764468.2764470","url":null,"abstract":"We study decentralized learning dynamics for the classic assignment game with transferable utility [Shapley and Shubik 1972]. In our model agents follow an aspiration adjustment process based on their experienced payoffs (see [Sauermann and Selten 1962], [Nax and Pradelski 2014]). At random points in time firms and workers match, break up, and re-match in the search for better opportunities. Agents have aspiration levels that they adjust based on their experienced payoffs. When matched an agent occasionally tries to succeed with a higher bid than his current aspiration level. When single an agent lowers his aspiration level in the hope of attracting a partner. In particular agents have no knowledge about other players' payoffs or actions and they update their behavior in a myopic fashion. Behavior fluctuates according to a random variable that reflects current market sentiment: sometimes the firms exhibit greater price stickiness than the workers, and at other times the reverse holds. We show that this stochastic learning process converges in polynomial time to the core. While convergence to the core is known for some types of decentralized dynamics this paper is the first to prove {polynomial time convergence}, a crucial feature from an explanatory and market design standpoint. We also show that without market sentiment the dynamic exhibits exponential time convergence. The proof relies on novel results for random walks on graphs, and more generally suggests a fruitful connection between the theory of random walks and matching theory.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116013495","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":"Hidden Substitutes","authors":"J. Hatfield, S. Kominers","doi":"10.1145/2764468.2764469","DOIUrl":"https://doi.org/10.1145/2764468.2764469","url":null,"abstract":"Substitutable preferences, i.e., preferences without complementarities, are necessary to guarantee the existence of stable outcomes in many market design settings. In this paper, we highlight a form of \"hidden substitutability\" that arises in many-to-one matching markets with contracts: some preferences over contracts that exhibit complementarity in fact have an underlying substitutable structure. Specifically, we show that some preferences that are not substitutable in the setting of many-to-one matching with contracts become substitutable when an employer is allowed to sign multiple contracts with an individual worker. These substitutably completable preferences guarantee the existence of stable contracting outcomes, even though stable outcomes are not guaranteed, in general, when complementarities are present. Our results imply the existence of a stable, strategy-proof mechanism for allocating workers with specialized skillsets; moreover, our results give new insight into the existing applications of matching with contracts to cadet--branch matching and the design of affirmative action programs.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127246603","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}