Nash Implementation and Uncertain Renegotiation

This paper studies Nash implementation when the outcomes of the mechanism can be renegotiated among the agents but the planner does not know the renegotiation function that they will use. We characterize the social objectives that can be implemented in Nash equilibrium when the same mechanism must work for every admissible renegotiation function. The constrained Walrasian correspondence, the core correspondence, and the Pareto-efficient and envy-free correspondence satisfy the necessary and sufficient conditions for this form of implementation if and only if freedisposal of the commodities is allowed. The uniform rule, on the other hand, is not Nash implementable for some admissible renegotiations functions.Implementation theory, Nash equilibrium, renegotiation function.

Contracting still matters! Or: How to design a letter of intent

Any cooperation that profits from relation-specific investments suffers from the well-known hold-up problem. If investments are not enforceable by an outside authority, the gains fall prey to individual opportunism caused by a free-rider problem. If, in addition, individual investments exhibit positive cross effects, Che and Hausch (1999) provide a negative result and show that contracts cannot overcome the hold up due to a lack of verifiable commitment. This paper develops a mechanism that provides such a commitment device: (1) It introduces an acknowledgement game that procures reliable. (2) It embeds the original contracting problem into two institutional designs - a market based one and a private design - that support enforcement. These two devices reestablish efficient investments as enforceable results of a contract.

IMPLEMENTATION WITH STATE DEPENDENT FEASIBLE SETS AND PREFERENCES: A RENEGOTIATION APPROACH

In this paper we present a model of implementation based on the idea that agents renegotiate unfeasible allocations. We characterize the maximal set of Social Choice Correspondences that can be implemented in Nash Equilibrium with a class of renegotiation functions that do not reward agents for unfeasibilities. This result is used to study the possibility of implementing the Walrasian Correspondence in exchange economies and several axiomatic solutions to problems of bargaining and bankruptcy.

Implementation with renegotiation when preferences and feasible sets are state dependent.

In this paper, we present a model of implementation where infeasible allocations are converted into feasible ones through a process of renegotiation that is represented by a reversion function. We describe the maximal set of Social Choice Correspondences that can be implemented in Nash Equilibrium in a class of reversion functions that punish agents for infeasibilities. This is used to study the implementation of the Walrasian Correspondence and several axiomatic solutions to problems of bargaining and taxation.Teoría de juegos; Toma de decisiones; Economía del bienestar;

The Hold-Up Problem and Incomplete Contracts: A Survey of Recent Topics in Contract Theory

This article provides a non-technical survey on recent topics in the theory of contracts. The hold-up problem is presented and the incomplete contracts approach is discussed. Emphasis is put on conceptual problems and open questions that await further research.Contract Theory; Hold-Up Problem; Incomplete Contracts

Agreeing Now to Agree Later: Contracts that Rule Out but do not Rule In

We view a contract as a list of outcomes. Ex ante, the parties commit not to consider outcomes not on the list, i. e. , these are “ruled out”. Ex post, they freely bargain over outcomes on the list, i. e. , the contract specifies no mechanism to structure their choice; in this sense outcomes on the list are not “ruled in”. A “loose” contract (long list) maximizes flexibility but may interfere with ex ante investment incentives. When these incentives are important enough, the parties may write a “tight” contract (short list), even though this leads to ex post inefficiency.

Agreeing Now to Agree Later: Contracts that Rule Out but do not Rule In

We view a contract as a list of outcomes. Ex ante, the parties commit not to consider outcomes not on the list, i.e., these are “ruled out”. Ex post, they freely bargain over outcomes on the list, i.e., the contract specifies no mechanism to structure their choice; in this sense outcomes on the list are not “ruled in”. A “loose” contract (long list) maximizes flexibility but may interfere with ex ante investment incentives. When these incentives are important enough, the parties may write a “tight” contract (short list), even though this leads to ex post inefficiency.

Agreeing Now to Agree Later: Contracts that Rule Out but do not Rule In

We view a contract as a list of outcomes. Ex ante, the parties commit not to consider outcomes not on the list, i.e., these are ruled out'. Ex post, they freely bargain over outcomes on the list, i.e., the contract specifies no mechanism to structure their choice; in this sense outcomes on the list are not ruled in'. A loose' contract (long list) maximizes flexibility but may interfere with ex ante investment incentives. When these incentives are important enough, the parties may write a tight' contract (short list), even though this leads to ex post inefficiency.

AGREEING NOW TO AGREE LATER: Contracts that Rule Out but do not Rule In

We view a contract as a list of outcomes. Ex ante, the parties commit not to consider outcomes not on the list, i.e., these are "ruled out". Ex post, they freely bargain over outcomes on the list, i.e., the contract specifies no mechanism to structure their choice; in this sense outcomes on the list are not "ruled out". A "loose" contract (long list) maximizes flexibility but may interfere with ex ante investment incentives. When these incentives are important enough, the parties may write a "tight" contract (short list), even though this leads to ex post inefficiency.Agreements to agree, ruling out but not ruling in, bargaining, ex post inefficiency.