The type-agent core for exchange economies with asymmetric information

The type-agent core is a new solution concept for exchange economies with asymmetric information. It coincides with the set of subgame-perfect equilibrium outcomes of a simple competitive screening game. Uninformed intermediaries help the agents to cooperate in an attempt to make some profit. The paper extends the work of Perez-Castrillo [Cooperative outcomes through non-cooperative games, Games Econ. Behav. 7 (1994) 428-440] to exchange economies with non-transferable utility and asymmetric information. The type-agent core is a subset of Wilson's coarse core [Wilson, Information, efficiency, and the core of an economy, Econometrica 46 (1978) 807-816]. It is never empty, even though it may be a strict subset of Wilson's fine core. In addition, it converges towards the set of constrained market equilibria as the economy is replicated.     

Cooperation through imitation

This paper characterizes long-run outcomes for broad classes of symmetric games, when players select actions on the basis of average historical performance. Received wisdom suggests that when agent's interests are partially opposed, behavior is excessively competitive: “keeping up with the Jones' ” lowers everyones' welfare. Here, we study the long-run consequences of imitative behavior when agents have sufficiently long memories and evaluate past actions in terms of (weighted) average payoff. Imitation robustly leads to cooperative outcomes (with highest symmetric payoffs) in the long run. Furthermore, lengthening memory reinforces this effect. This provides a rationale, for example, for collusive cartel-like behavior without collusive intent.     

Competitive behavior in market games: Evidence and theory

We explore whether competitive outcomes arise in an experimental implementation of a market game, introduced by Shubik (1973) [21]. Market games obtain Pareto inferior (strict) Nash equilibria, in which some or possibly all markets are closed. We find that subjects do not coordinate on autarkic Nash equilibria, but favor more efficient Nash equilibria in which all markets are open. As the number of subjects participating in the market game increases, the Nash equilibrium they achieve approximates the associated competitive equilibrium of the underlying economy. Motivated by these findings, we provide a theoretical argument for why evolutionary forces can lead to competitive outcomes in market games.     

Commitment and observability in a contracting environment

This paper examines leader-follower games where a leader must purchase an essential input from a price-setting supplier in order to take an action. We show that equilibrium outcomes when the followers perfectly observe the leaders' actions cannot be approximated by mixed equilibrium outcomes of the game where followers imperfectly observe the leaders' actions, i.e. they are not accessible. Accessibility fails since in a pure strategy equilibrium, a supplier makes positive profits; however in an equilibrium where a leader randomizes, supplier profits must be zero. Our result follows from a generalized indifference principle that mixed strategies must satisfy in economic environments. While supplier profits cannot be approximated, player action profiles are accessible. Our results also apply to games with costly observation.     

Competitive outcomes and the inner core of NTU market games

We consider the inner core as a solution concept for cooperative games with non-transferable utility (NTU) and its relationship to payoffs of competitive equilibria of markets that are induced by NTU games. An NTU game is an NTU market game if there exists a market such that the set of utility allocations a coalition can achieve in the market coincides with the set of utility allocations the coalition can achieve in the game. In this paper, we introduce a new construction of a market based on a closed subset of the inner core which satisfies a strict positive separability. We show that the constructed market represents the NTU game and, further, has the given closed set as the set of payoff vectors of competitive equilibria. It turns out that this market is not uniquely determined, and thus, we obtain a class of markets. Our results generalize those relating to competitive outcomes of NTU market games in the literature.     

Payoffs in Nondifferentiable Perfectly Competitive TU Economies

We show that a single-valued solution of nonatomic finite-type market games (or perfectly competitive TU economies underling them) is uniquely determined as the Mertens value by four plausible value-related axioms. Since the Mertens value is always in the core of an economy, this result provides an axiomatization of a core-selection (or, alternatively, a competitive payoff selection). Journal of Economic Literature Classification Numbers: C71, D51, D61.     

Asymmetric and endogenous within-group communication in competitive coordination games

Within-group communication in competitive coordination games has been shown to increase competition between groups and lower efficiency. This study further explores potentially harmful effects of communication, by addressing the questions of (1) asymmetric communication and (2) the endogenous emergence of communication. Our theoretical analysis provides testable hypotheses regarding the effect of communication on competitive behavior and efficiency. We test these predictions using a laboratory experiment. The experiment shows that although asymmetric communication is not as harmful as symmetric communication, it leads to more aggressive competition and lower efficiency relative to the case when neither group can communicate. Moreover, groups vote to endogenously establish communication channels even though they would earn higher payoffs if jointly they chose to restrict within-group communication.     

On Norms and Coordination Games: A Rent–Seeking Approach

The aim of this paper is to extend the rent–seeking literature to the equilibrium selection problem in competitive coordination games, i.e., games in which more than one equilibrium exists, and individuals' preferences are opposed. We analyze alternative correlated equilibria: contractual agreements and legally enforced equilibria. The latter are to be understood as the outcome of rents–seeking contests in which players invest resources in order to set a norm. The contest is analyzed in its basic two–person setting and later generalized to the two–populations case. There we show that the outcomes depend on the relative payoff structure of the game, the technological properties of the contest, and the population distribution. Finally, the efficiency analysis focuses not only on the extent of the rent dissipation, but also on the comparative analysis of the inefficiencies that arise in the market (not coordinated) equilibrium.     

Asymmetric equilibria under price cap regulation

This study analyzes the effects of a price-cap regulation on market outcomes in Cournot and Stackelberg duopolies. Although two firms are ex-ante identical, there are asymmetric Cournot equilibria as well as the symmetric equilibrium under the price-cap regulation, when the price-cap level is binding. By contrast, the Stackelberg equilibrium is unique and equivalent to the most asymmetric Cournot equilibrium under a binding price-cap level. We present several comparative statics results with respect to the equilibrium outcomes. The main concern of this study is the welfare effect of a change in a price-cap level. We show that when asymmetric Cournot equilibria or the Stackelberg equilibrium are focused on, a reduction in a price-cap level may be socially harmful even if the price-cap level is more than the competitive price.     

Uncertainty and insurance in strategic market games

Summary. For perfectly competitive economies under uncertainty, there is a well-known equivalence between a formulation with contingent goods and one with state-specific securities followed by spot markets for goods. In this paper, I examine whether this equivalence carries over to a particular form of imperfect competition. Specifically, I look at three Shapley-Shubik strategic market games: one with contingent commodities, one with Arrow securities traded under imperfect competition and one with Arrow securities traded under perfect competition. First I compare the feasibility constraints of these three games. Then I compare their equilibrium sets. As in Peck and Shell (1989), the only common equilibria between the first and the second game are those which involve no transfer of income across states. However, if the securities markets are competitive, then the set of equilibria of the contingent commodities game and the securities game coincide. Received: June 16, 1997; revised version: April 30, 1998     

Competitive environments and protective behavior

The class of two-person competition games is introduced and analyzed. For any game in this class the set of Nash equilibria is convex and all Nash equilibria lead to the same payoff vector. Competition games are compared to other competitive environments such as unilaterally competitive games and rivalry games. Moreover, protective behavior within competitive environments is analyzed. For matrix games it is known that protective strategies profiles exactly correspond to proper equilibria. It is shown that this result can be extended to the class of unilaterally competitive games.     

On the Irrelevance of Risk Attitudes in Repeated Two-Outcome Games

We study equilibrium and maximin play in supergames consisting of the sequential play of a finite collection of stage games, where each stage game has two outcomes for each player. We show that for two-player supergames in which each stage game is strictly competitive, in any Nash equilibrium of the supergame, play at each stage is a Nash equilibrium of the stage game provided preferences over certain supergame outcomes satisfy a natural monotonicity condition. In particular, equilibrium play does not depend on risk attitudes. We establish an invariance result for games with more than two players when the solution concept is subgame perfection. Journal of Economic Literature Classification Numbers: C72, C9.     

Bargaining and Sharing Innovative Knowledge

We consider the problem of bargaining over the disclosure of interimresearch knowledge between two participants in an R&D race for an ultimate,patentable invention. Licence fee schedules that are functions of the'amount of knowledge disclosed', by the leading to the laggingagent, are examined for their abilities to attain efficient outcomes andvarying shares of the surplus arising from disclosure. In hersequential-offers bargaining games, the uninformed buyer is able to elicitfull disclosures without sharing the incremental surplus with any type ofthe licensor, and thus do as well as a perfectly informed and discriminatingknowledge licensee.     

Market games with asymmetric information: the core

This paper concerns cores of economies with asymmetric information. Alternative definitions of the information available to traders in coalitions and the cooperative games they generate are analyzed. An important technical result states that such NTU games in characteristic function form are well defined. Properties of various cores with asymmetric information are examined. Sufficient conditions on information sharing rules are provided for the induced games to be totally balanced or balanced, so that their cores are nonempty. Incentive compatibility issues are considered. Finally, a perspective on this research area is provided.     

Modelling non-competitive behavior in commodity markets: A game theoretic approach

In this paper, we provide a coalitional alternative to the perfectly competitive and purely non-cooperative assumptions commonly employed in the modelling of commodity markets. These assumptions of perfect competition or pure non-cooperation are usually imposed exogenously without providing an economic basis for assuming why firms that could stand to gain by cooperating would not in fact do so. Three behavioral rules embodied in three different cooperative games are discussed in this paper and a methodology for predicting the coalition structures that would result from each of these is offered. By applying these games to the US copper industry of the 1970's, we show that the theory of games can be profitably employed in conjunction with the traditional institutional approach of industrial organization to yield useful economic predictions.The author is grateful to two anonymous referees whose comments led to a considerably improved version of the paper.     

Perfect competition in asymmetric information economies: compatibility of efficiency and incentives

The idea of perfect competition for an economy with asymmetric information is formalized via an idiosyncratic signal process in which the private signals of almost every individual agent can influence only a negligible group of agents, and the individual agents’ relevant signals are essentially pairwise independent conditioned on the true states of nature. Thus, there is no incentive for an individual agent to manipulate her private information. The existence of incentive compatible, ex post Walrasian allocations is shown for such a perfectly competitive asymmetric information economy with or without “common values”. Consequently, the conflict between incentive compatibility and Pareto efficiency is resolved exactly, and its asymptotic version is derived for a sequence of large, but finite private information economies.     

Evolutionary stability of discrimination under observability

We study the evolution of preferences under perfect and almost perfect observability in symmetric 2-player games. We demonstrate that if nature can choose from a sufficiently general preference space, which includes preferences over outcomes that may depend on the opponent's preference-type, then, in most games, only discriminating preferences (treating different types of opponents differently in the same situation) can be evolutionary stable and some discriminating types are stable in a very strong sense in all games. We use these discriminating types to show that any symmetric outcome which gives players more than their minmax value in material payoffs (fitness) can be seen as equilibrium play of a player population with such strongly stable preferences.     

Contracts without memory in multiperiod agency models

Settings are considered in which optimal multiperiod contracts can have no memory, i.e., where second period payments do not need to depend on first period outcomes. If contracts have no memory, a repeated agency game can be played myopically; there are no gains to long-term relationships. Conditions on preferences for a no memory contract are presented. In an agency game with moral hazard on the act selection, preference separability and domain additivity imply the existence of a no memory contract. In a setting without moral hazard but with asymmetric information on the outcome, domain additivity implies no memory.     

Evolutionary stability of discrimination under observability

We study the evolution of preferences under perfect and almost perfect observability in symmetric 2-player games. We demonstrate that if nature can choose from a sufficiently general preference space, which includes preferences over outcomes that may depend on the opponent's preference-type, then, in most games, only discriminating preferences (treating different types of opponents differently in the same situation) can be evolutionary stable and some discriminating types are stable in a very strong sense in all games. We use these discriminating types to show that any symmetric outcome which gives players more than their minmax value in material payoffs (fitness) can be seen as equilibrium play of a player population with such strongly stable preferences.     

Oligopoly with a large number of competitors: asymmetric limit result

We address how profitable innovation is in a competitive market by investigating the asymmetric oligopoly model in which 1 firm (innovator) has a cost advantage that is not drastic enough for her to become a monopolist, and by inducing asymmetric limit outcomes when the number of the other firms (laggard firms) goes to infinity. If the innovator is the Stackelberg leader, two cases can arise: (i) the innovator behaves as in the competitive market or (ii) she occupies the entire market but cannot make the price. If we consider Cournot competition, the innovator becomes the partial monopolist. An erratum to this article can be found at