Gwenaël Piaser

On multiple-principal multiple-agent models of moral hazard

We provide two examples in a pure moral hazard setting with two principals and two agents. Example 1 shows that a strongly robust equilibrium in simple (direct) mechanisms can no longer be sustained as an equilibrium when a principal can deviate to an indirect communication scheme. Conversely, an equilibrium with one principal offering an indirect mechanism cannot be replicated as an equilibrium in simple mechanisms. Example 2 shows more directly that a payoff profile that can be achieved in equilibrium when one principal offers an indirect mechanism cannot be achieved as an equilibrium profile in simple mechanisms.

Multiple Lending and Constrained Efficiency in the Credit Market

In this paper we present a model of credit market with several homogeneous lenders competing to finance an investment project. Contracts are non-exclusive, hence the borrower can accept whatever subset of the offered loans. We use the model to discuss efficiency issues in competitive economies with asymmetric information and non-exclusive agreements. We characterize the equilibria of this common agency game with moral hazard and show that they all belong to the constrained Pareto frontier.

Common Agency Games with Separable Preferences

This paper examines the role of the revelation principle in common agency games. We show how the introduction of a separability condition on the preferences of the agent is sufficient for the revelation principle to hold. Therefore, it is still possible to restrict attention to direct mechanisms without any loss of generality even when competition over contracts is considered.

A Note on Common Agency Models of Moral Hazard

We consider Common Agency games of moral hazard and we suggest that there is only a very weak support for the standard restriction to take-it or leave-it contracts.

Information Revelation in Competing Mechanism Games

We consider multiple-principal multiple-agent games of incomplete information. In this context, we identify a class of direct and incentive compatible mechanisms: each principal privately recommends to each agent to reveal her private information to the other principals, and each agent behaves truthfully. We show that there is a rationale in restricting attention to this class of mechanisms: if all principals make use of direct incentive compatible mechanisms, there are no incentives to unilaterally deviate towards more sophisticated mechanisms. We develop two examples to show that private recommendations are a key element of our construction, and that the restriction to direct incentive compatible mechanisms is not sufficient to provide a complete characterization of equilibria.

Competing Mechanisms, Exclusive Clauses and the Revelation Principle

We consider multiple-principal multiple-agent games of incomplete information in which each agent can at most participate with one principal. In such contexts, we show that the restriction to direct truthful mechanisms involves a loss of generality, even if one only focuses on pure strategy equilibria. However, the traditional Revelation Principle retains its power in games with a single agent.

Vaccination versus ‘wait and treat’: how to subsidize them?

In this paper we discuss the application of different co-payment rates to alternative medical strategies. Two such strategies are considered: a “vaccination strategy”, in which patients apply preventive measures before knowing if they have the disease, and a “wait and treat” strategy, in which patients are treated later only if they contract the disease. We show the second approach should be more generously subsidized by the regulator. This is, at least at first sight, a surprising result.

On Competing Mechanisms under Exclusive Competition

We study games in which several principals design mechanisms in the presence of privately informed agents. Competition is exclusive: each type of each agent can participate with at most one principal and meaningfully communicate only with him. Economic models of exclusive competition restrict principals to use standard direct mechanisms, which induce truthful revelation of agents’ exogenous private information. This paper investigates the rationale for this restriction. We provide two results. First, we construct examples showing that direct mechanisms fail to completely characterize equilibrium outcomes even if we restrict to pure strategy equilibria. Second, we show that truth-telling strongly robust equilibrium outcomes survive against principals’ unilateral deviations toward arbitrary mechanisms. (This abstract was borrowed from another version of this item.)

On Private Communication in Competing Mechanism Games

We study competing mechanism games in which principals simultaneously design contracts to deal with several agents. We show that principals can profit from privately communicating with agents by generating incomplete information in the continuation game they play. Specifically, we construct an example of a complete information game in which none of the (multiple) equilibria in Yamashita (2010) survives against unilateral deviations to mechanisms involving private communication. This also contrasts with the robustness result established by Han (2007). The role of private communication we document may call for extending the standard construction of Epstein and Peters (1999) to incorporate this additional element.