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":"Procurement Mechanisms for Differentiated Products","authors":"D. Sabán, G. Weintraub","doi":"10.1145/2764468.2764520","DOIUrl":"https://doi.org/10.1145/2764468.2764520","url":null,"abstract":"We consider the problem faced by a procurement agency that runs an auction-type mechanism to construct an assortment of products with posted prices, from a set of differentiated products offered by strategic suppliers. Heterogeneous consumers then buy their most preferred alternative from the assortment as needed. Framework agreements (FAs), widely used in the public sector, take this form; the central government runs the initial auction and then the public organizations (hospitals, schools, etc.) buy from the selected assortment. This type of mechanism is also relevant in other contexts, such as the design of medical formularies and group buying. When evaluating the bids, the procurement agency must consider the optimal trade-off between offering a richer assortment of products for consumers versus offering less variety, hoping to engage the suppliers in a more aggressive price competition. We develop a mechanism design approach to study this problem and provide a characterization of the optimal assortments and prices. The optimal mechanism balances the trade-off between product variety and price competition, in terms of suppliers' costs, products' characteristics, and consumers' characteristics. Relative to the traditional mechanism design problem, a distinctive feature of our formulation is that the auctioneer cannot directly decide how to allocate demand across products. Instead, the auctioneer selects the assortment and prices, and demands are then determined by the underlying preferences of consumers. Our work advances the theory of auctions and mechanism design by accounting for an endogenous demand system for differentiated products. We then use the optimal mechanism as a benchmark to evaluate the performance of the Chilean government procurement agency's current implementation of FAs, used to acquire US$2 billion worth of goods per year. We show how simple modifications to the current mechanism, which increase price competition among close substitutes, can considerably improve performance.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"123 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":"134601748","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":"Commitment Without Regrets: Online Learning in Stackelberg Security Games","authors":"Maria-Florina Balcan, Avrim Blum, Nika Haghtalab, A. Procaccia","doi":"10.1145/2764468.2764478","DOIUrl":"https://doi.org/10.1145/2764468.2764478","url":null,"abstract":"In a Stackelberg Security Game, a defender commits to a randomized deployment of security resources, and an attacker best-responds by attacking a target that maximizes his utility. While algorithms for computing an optimal strategy for the defender to commit to have had a striking real-world impact, deployed applications require significant information about potential attackers, leading to inefficiencies. We address this problem via an online learning approach. We are interested in algorithms that prescribe a randomized strategy for the defender at each step against an adversarially chosen sequence of attackers, and obtain feedback on their choices (observing either the current attacker type or merely which target was attacked). We design no-regret algorithms whose regret (when compared to the best fixed strategy in hindsight) is polynomial in the parameters of the game, and sublinear in the number of times steps.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"33 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":"131671059","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":"Simple Auctions with Simple Strategies","authors":"Nikhil R. Devanur, Jamie Morgenstern, Vasilis Syrgkanis, S. Weinberg","doi":"10.1145/2764468.2764484","DOIUrl":"https://doi.org/10.1145/2764468.2764484","url":null,"abstract":"We introduce single-bid auctions as a new format for combinatorial auctions. In single-bid auctions, each bidder submits a single real-valued bid for the right to buy items at a fixed price. Contrary to other simple auction formats, such as simultaneous or sequential single-item auctions, bidders can implement no-regret learning strategies for single-bid auctions in polynomial time. Price of anarchy bounds for correlated equilibria concepts in single-bid auctions therefore have more bite than their counterparts for auctions and equilibria for which learning is not known to be computationally tractable (or worse, known to be computationally intractable [Cai and Papadimitriou 2014; Dobzinski et al. 2015] this end, we show that for any subadditive valuations the social welfare at equilibrium is an O(log m)-approximation to the optimal social welfare, where $m$ is the number of items. We also provide tighter approximation results for several subclasses. Our welfare guarantees hold for Nash equilibria and no-regret learning outcomes in both Bayesian and complete information settings via the smooth-mechanism framework. Of independent interest, our techniques show that in a combinatorial auction setting, efficiency guarantees of a mechanism via smoothness for a very restricted class of cardinality valuations extend, with a small degradation, to subadditive valuations, the largest complement-free class of valuations.","PeriodicalId":376992,"journal":{"name":"Proceedings of the Sixteenth ACM Conference on Economics and Computation","volume":"35 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":"116920149","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}