Coalition Formation and Potential Games

In this paper we study the formation of coalition structures in situations described by a cooperative game. Players choose independently which coalition they want to join. The payoffs to the players are determined by an allocation rule on the underlying game and the coalition structure that results from the strategies of the players according to some formation rule. We study two well-known coalition structure formation rules and show that for both formation rules there exists a unique component-efficient allocation rule that results in a potential game. Journal of Economic Literature Classification Numbers: C71, C72.     

Disappearing private reputations in long-run relationships

For games of public reputation with uncertainty over types and imperfect public monitoring, Cripps et al. [Imperfect monitoring and impermanent reputations, Econometrica 72 (2004) 407-432] showed that an informed player facing short-lived uninformed opponents cannot maintain a permanent reputation for playing a strategy that is not part of an equilibrium of the game without uncertainty over types. This paper extends that result to games in which the uninformed player is long-lived and has private beliefs, so that the informed player's reputation is private. The rate at which reputations disappear is uniform across equilibria and reputations also disappear in sufficiently long discounted finitely repeated games.     

A note on the core of an income redistribution game

We consider a redistribution of income by an n-person game in which each member is levied a proportional income tax under some fixed rule. It is shown that the redistribution that will be achieved by a specific negative income tax is in the core of the game, which means that the redistribution can not be upset by any coalition of members acting strategically to evade the full taxation.     

Sharing the surplus: An extension of the Shapley value for environments with externalities

Economic activities, both on the macro and micro level, often entail wide-spread externalities. This in turn leads to disputes regarding the compensation levels to the various parties affected. We propose a method of deciding upon the distribution of the gains (costs) of cooperation in the presence of externalities when forming the grand coalition is efficient. We show that any sharing rule satisfying efficiency, linearity, dummy player and a strong symmetry axioms can be obtained through an average game. Adding an additional axiom, we identify one unique rule satisfying these properties.     

Stable Coalition Structures with Externalities

This paper argues that the sign of external effects of coalition formation provides a useful organizing principle in examining economic coalitions. In many interesting economic games, coalition formation creates eithernegativeexternalities orpositiveexternalities for nonmembers. Examples of negative externalities are research coalitions and customs unions. Examples of positive externalities include output cartels and public goods coalitions. I characterize and compare stable coalition structures under the following three rules of coalition formation: the Open Membership game of Yi and Shin (1995), the Coalition Unanimity game of Bloch (1996), and the Equilibrium Binding Agreements of Ray and Vohra (1994).Journal of Economic LiteratureClassification Numbers: C72, C71.     

集体信誉的理论分析——组织内部逆向选择问题

建立在重复博弈模型上的逆向选择问题称为信誉理论,该理论主要研究博弈参与者如何通过树立信誉实现在非合作博弈中的合作均衡。传统的信誉理论涉及的多是个体的信誉问题,但是当个体信息无法传递时,个体信誉便无法发挥作用。此时,公众通常会对拥有相同标识的集体形成一个整体判断,与个体利益相关的是他们拥有的集体信誉。本文考察了集团内部存在不同类型个体时集体信誉维护的问题,本文称为内部逆向选择问题。我们发现,由于个体利益与集体利益的差异,导致集体信誉的激励作用要弱于传统的个体信誉的作用。此外,由于集体利益与社会利益的不一致,最终即使可以有效激励集团成员最大限度地维护集体利益,如果公众信念更新相对麻木,仍会造成经济运行无效率。     

Corruption and Reputation

This paper examines corruption in a random matching game where past actions are imperfectly observed and players have the option to continue trading with their existing partners. It shows that the effect of individual reputations for honesty may outweigh the effect of a bad collective reputation depending on the expected value of a continued match relative to the corruption gain.     

THE DETERMINANTS OF PRICE IN ONLINE AUCTIONS: MORE EVIDENCE FROM QUANTILE REGRESSION

This study explores how seller reputations affect auction prices and concludes that earlier findings may be biased due to the misspecification of seller reputation. This paper contributes to the literature by offering significant empirical evidence using Taiwanese internet auction data. Our study reveals that the influence of seller reputations on auction prices is significant, irrespective of the assumptions of linear or non‐linear relationships with price. However, failure to consider the non‐linear setting of seller reputation leads us to underestimate the impact of reputation when the seller's reputation score is low, but overestimates it when the seller's reputation becomes high. Using quantile regression, this study finds evidence of considerable differences in their impact on auction prices that are dependent on the distribution of price levels.     

Who Wants a Good Reputation?

We examine a market in which long-lived firms face a short-term incentive to exert low effort, but could earn higher profits if it were possible to commit to high effort. There are two types of firms, "inept" firms who can only exert low effort, and "competent" firms who have a choice between high and low effort. There is occasional exit, and competent and inept potential entrants compete for the right to inherit the departing firm's reputation. Consumers receive noisy signals of effort choice, and so competent firms choose high effort in an attempt to distinguish themselves from inept firms. A competent firm is most likely to enter the market by purchasing an average reputation, in the hopes of building it into a good reputation, than either a very low reputation or a very high reputation. Inept firms, in contrast, find it more profitable to either buy high reputations and deplete them or buy low reputations.     

A game-theoretic model of coalition formation among primates

This paper models the coalition formation process among primates as a sequential game. The population consists of individuals having distinct social ranks which is determined by the individual’s resource holding potential. Each member of the population is interested in gaining access to a food resource, either individually or via a coalition. At any given stage of the game, a player can either propose a specific coalition or he can be proposed to in order to join one. Hence, the strategy of a player consists of a sequence of decisions regarding who to propose to for the formation of a coalition and which proposals to accept or reject. We derive the preferences of the players over the various coalition structures under the assumption that the probability of a coalition to obtain the resource is given by a logistic distribution as a function of relative strengths of the players. We show that, given the primates’ strategic behavior, a variety of different coalition structures can emerge in equilibrium.      

On the core of economies with multilateral environmental externalities

We revisit the cooperative model of coalition formation in economies with environmental externalities. Motivated by recent concerns over the true behavior and incentives of key players in international negotiations over the climate and the environment, we construct a cooperative game where the members of each coalition have uncertainty over the behavior of the nonmembers, and in particular they face uncertainty over their coalition structure. As a result, a coalition assigns various probability distributions over the set of partitions the outsiders can form. We compute the payoff of each coalition under this assumption and we derive conditions under which the core of the induced cooperative game is nonempty.     

Audited reputation

We study reputations with imperfect audit and a reputation market. The main result shows the existence of a separating equilibrium in the reputation market, which contrasts with Tadelis [Tadelis, S., 2002, The market for reputations as an incentive mechanism, Journal of Political Economy 110(4), 854–882].     

Tactical distribution in local funding: The value of an aligned mayor

Using Chile as a case study for understanding tactical distribution under extensive controls on expenditure, this paper examines whether political motives affect the allocation of funds from the central government to localities. Collecting local-level data of two infrastructure funding programs and using the voting gap percentage between the coalition candidate and opposition competitors in a Sharp Regression Discontinuity methodology, we find causal evidence in favor of three hypotheses: (i) a coalition criterion influences the funding allocation to the local level; (ii) an electoral cycle exists in local funding; and (iii) the degree of coalition targeting varies based on a locality's history of coalition alignment. In sum, the central government regards politically aligned mayors as valuable electoral assets, especially in municipalities historically aligned with the coalition.     

Strongly stable networks

We analyze the formation of networks among individuals. In particular, we examine the existence of networks that are stable against changes in links by any coalition of individuals. We show that to investigate the existence of such strongly stable networks one can restrict focus on a component-wise egalitarian allocation of value. We show that when such strongly stable networks exist they coincide with the set of efficient networks (those maximizing the total productive value). We show that the existence of strongly stable networks is equivalent to core existence in a derived cooperative game and use that result to characterize the class of value functions for which there exist strongly stable networks via a “top convexity” condition on the value function on networks. We also consider a variation on strong stability where players can make side payments, and examine situations where value functions may be non-anonymous—depending on player labels.     

Trust, reputation and relationships in grazing rights markets: An experimental economic study

Trust is frequently a requirement for economic exchanges and the management of natural resources. Providing public information on past actions can promote trust through the formation of reputations. We developed an economic experiment to test whether a formal reputation mechanism could facilitate trusting relationships in the tradable grazing rights markets. Providing information to create formal public reputations for market participants did not increase the overall efficiency of the market. However, it did result in greater equality of income between partners, suggesting that participants showed more concern for their partners when they knew they would be rated. Even with public reputation information, bilateral relationships remained central to the market. Market failures in existing grazing rights markets may be better addressed by measures to increase communication between partners rather than simply relying on a formal reputation mechanism.     

Forming and Dissolving Partnerships in Cooperative Game Situations

A group of players in a cooperative game are partners (e.g., as in the form of a union or a joint ownership) if the prospects for cooperation are restricted such that cooperation with players outside the partnership requires the accept of all the partners. The formation of such partnerships through binding agreements may change the game implying that players could have incentives to manipulate a game by forming or dissolving partnerships. The present paper seeks to explore the existence of allocation rules that are immune to this type of manipulation. An allocation rule that distributes the worth of the grand coalition among players is called partnership formation‐proof if it ensures that it is never jointly profitable for any group of players to form a partnership and partnership dissolution‐proof if no group can ever profit from dissolving a partnership. The paper provides results on the existence of such allocation rules for general classes of games as well as more specific results concerning well‐known allocation rules.     

On choosing which game to play when ignorant of the rules

This paper suggests a theory of choice among strategic situations when the rules of play are not properly specified. We take the view that a “strategic situation” is adequately described by a TU game since it specifies what is feasible for each coalition but is silent on the procedures that are used to allocate the surplus. We model the choice problem facing a decision maker (DM) as having to choose from finitely many “actions”. The known “consequence” of the ith action is a coalition from game f _i over a fixed set of players \(N_i\cup\{d\}\) (where d stands for the DM). Axioms are imposed on her choice as the list of consequences (f ₁,..., f _m ) from the m actions varies. We characterize choice rules that are based on marginal contributions of the DM in general and on the Shapley Value in particular.     

Values for Markovian coalition processes

Time series of coalitions (so-called scenarios) are studied that describe processes of coalition formation where several players may enter or leave the current coalition at any point in (discrete) time and convergence to the grand coalition is not necessarily prescribed. Transitions from one coalition to the next are assumed to be random and to yield a Markov chain. Three examples of such processes (the Shapley-Weber process, the Metropolis process, and an example of a voting situation) and their properties are presented. A main contribution includes notions of value for such series, i.e., schemes for the evaluation of the expected contribution of a player to the coalition process relative to a given cooperative game. Particular processes permit to recover the classical Shapley value. This methodology??s power is illustrated with well-known examples from exchange economies due to Shafer (Econometrica 48:467?C476, 1980) and Scafuri and Yannelis (Econometrica 52:1365?C1368, 1984), where the classical Shapley value leads to counterintuitive allocations. The Markovian process value avoids these drawbacks and provides plausible results.     

Designing international environmental agreements under participation uncertainty

Traditional international environmental agreement (IEA) models usually use some specific contribution rules, which either fail to provide sufficient incentives for cooperation, or ignore the loss from participation uncertainty. Can more general rules overcome these problems and improve the performance of IEAs? This paper analyzes the endogenous determination of contribution rules from a class of general rules through a three-stage coalition formation game under participation uncertainty. In stage one, a designer chooses a contribution rule, which, depending on the size of the signatories’ coalition formed in stage two, specifies the action each signatory should take in stage three. A contribution rule is said to be optimal when it maximizes the expected payoff of signatories. We provide an algorithm to determine an optimal rule. When uncertainty is either sufficiently large or equal to zero, the optimal rule coincides with some existing rules in the literature. However, when the uncertainty is neither large nor small, the optimal rule outperforms other rules in terms of signatories’ payoff.     

声誉、搜寻成本与网上交易市场均衡

本文在搜寻理论的框架内分析了在卖家声誉存在差异的情况下,网上拍卖市场搜寻成本对价格水平和价格离差的影响,进而考察了搜寻成本对网上市场声誉机制的影响。本文的结论是:尽管搜索工具提高了网上交易市场的效率,但网上交易市场仍存在不可忽视的搜寻成本;较高的搜寻成本导致不同声誉水平的卖家同时存在于网上交易市场,高声誉卖家制定的价格较高,低声誉卖家制定的价格较低;搜寻效率的提高可以降低均衡价格水平,网站提供的推广服务也可以降低搜寻成本,降低均衡价格水平。模型很好地解释了网上拍卖市场中的一些现象,也与最近文献的经验事实有较好的吻合。