Communication, Renegotiation and Coordination with Private Values (Extended Version)

An equilibrium is communication-proof if it is unaffected by new opportunities to communicate and renegotiate. We characterize the set of equilibria of coordination games with pre-play communication in which players have private preferences over the feasible coordinated outcomes. Communication-proof equilibria provide a narrow selection from the large set of qualitatively diverse Bayesian Nash equilibria in such games. Under a communication-proof equilibrium, players never miscoordinate, play their jointly preferred outcome whenever there is one, and communicate only the ordinal part of their preferences. Moreover, such equilibria are robust to changes in players' beliefs, interim Pareto efficient, and evolutionarily stable.Comment:

Mechanism Design and Non-Cooperative Renegotiation

We characterize decision rules which are implementable in mechanism design settings when, after the play of a mechanism, the uninformed party can propose a new mechanism to the informed party. The necessary and sufficient conditions are, essentially, that the rule be implementable with commitment, that for each type the decision is at least as high as if there were no mechanism, and that the slope of the decision function is not too high. The direct mechanism which implements such a rule with commitment will also implement it in any equilibrium without commitment, so the standard mechanism is robust to renegotiation

The Theory of Implementation of Social Choice Rules

Suppose that the goals of a society can be summarized in a social choice rule, i.e., a mapping from relevant underlying parameters to final outcomes. Typically, the underlying parameters (e.g., individual preferences) are private information to the agents in society. The implementation problem is then formulated: under what circumstances can one design a mechanism so that the private information is truthfully elicited and the social optimum ends up being implemented? In designing such a mechanism, appropriate incentives will have to be given to the agents so that they do not wish to misrepresent their information. The theory of implementation or mechanism design formalizes this “social engineering” problem and provides answers to the question just posed. I survey the theory of implementation in this article, emphasizing the results based on two behavioral assumptions for the agents (dominant strategies and Nash equilibrium). Examples discussed include voting, and the allocation of private and public goods under complete and incomplete information.Implementation Theory, Mechanism Design, Asymmetric Information, Decentralization, Game Theory, Dominance, Nash Equilibrium, Monotonicity

Strategic interaction between futures and spot markets.

There is a literature (e.g., Allaz and Vila, 1992 and Hughes and Kao, 1997) showing that in an oligopolistic context, the presence of a futures market induces firms to use it in order to increase its market share. The consequence of this behavior is that the total quantity supplied by the industry increases, thus making the oligopolistic outcome closer to the competitive equilibrium. In the present work, we propose a model to study the interaction of spot and futures markets that does not imply this pro-competitive effect. The model is the same as in Allaz and Vila in the sense that firms have infinitely many moments to trade in the futures market before the spot market takes place. We analyze the equilibria in the infinite case directly and show that many equilibria emerge in a kind of folk-theorem result (but ours is not a repeated game). The equilibrium in which firms do not use the forward market is particularly robust as it satisfies the most demanding definition of renegotiation-proofuess. Furthermore, if firms are allowed to buy in the futures market, they can sustain the monopolistic outcome in a renegotiation-proof equilibrium (notice that there is only one period in the spot market). We also study the role of information in the model and argue that our results fit better stylized facts of some industries like the power market in the U.K.Futures markets; Cournot competition; Collusion;

Implementation in Bayesian Equilibrium: The Multiple Equilibrium Problem in Mechanism Design

This paper surveys the literature on implementation in Bayesian Equilibrium

Strategic interaction between futures and spot markets

We study an oligopolistic industry where firms are able to sell in a futures market at infinitely many moments prior to the spot market. A kind of Folk-theorem is established: any outcome between perfect competition and Cournot can be sustained in equilibrium. We then find that the Cournot outcome can be sustained by a renegotiation-proof equilibrium. However, this is not true for the competitive outcome. Furthermore, only the monopolistic outcome is renegotiation-proof if firms can buy and sell in the futures market. These results suggest, contrary to existing literature, that the introduction of futures markets may have an anti-competitive effect.Financial support from DGESIC Grant PB-98/0024 (Ministerio de Educación y Cultura) is gratefully acknowledged.Publicad