Andrea Attar

Nonexclusive Competition in the Market for Lemons

We consider an exchange economy in which a seller can trade an endowment of a divisible good whose quality she privately knows. Buyers compete in menus of non-exclusive contracts, so that the seller may choose to trade with several buyers. In this context, we show that an equilibrium always exists and that aggregate equilibrium allocations are generically unique. Although the good offered by the seller is divisible, aggregate equilibrium allocations exhibit no fractional trades. In equilibrium, goods of relatively low quality are traded at the same price, while goods of higher quality may end up not being traded at all if the adverse selection problem is severe. This provides a novel strategic foundation for Akerlof’s (1970) results, which contrasts with standard competitive screening models postulating enforceability of exclusive contracts. Latent contracts that are issued but not traded in equilibrium turn out to be an essential feature of our construction.(This abstract was borrowed from another version of this item.)

Non-Exclusive Competition in the Market for Lemons

We consider an exchange economy in which a seller can trade an endowment of a divisible good whose quality she privately knows. Buyers compete in menus of non-exclusive contracts, so that the seller may choose to trade with several buyers. In this context, we show that an equilibrium always exists and that aggregate equilibrium allocations are generically unique. Although the good offered by the seller is divisible, aggregate equilibrium allocations exhibit no fractional trades. In equilibrium, goods of relatively low quality are traded at the same price, while goods of higher quality may end up not being traded at all if the adverse selection problem is severe. This provides a novel strategic foundation for Akerlofs (1970) results, which contrasts with standard competitive screening models postulating enforceability of exclusive contracts. Latent contracts that are issued but not traded in equilibrium turn out to be an essential feature of our construction.

Non-Exclusive Competition Under Adverse Selection

A seller of a divisible good faces several identical buyers. The quality of the good may be low or high, and is the sellers private information. The seller has strictly convex preferences that satisfy a single-crossing property. Buyers compete by posting menus of nonexclusive contracts, so that the seller can simultaneously and privately trade with several buyers. We provide a necessary and sufficient condition for the existence of a pure-strategy equilibrium. Aggregate equilibrium trades are unique. Any traded contract must yield zero profit. If a quality is actually traded, then it is efficiently traded. Depending on parameters, both qualities may be traded, or only one of them, or the market may break down to a no-trade equilibrium.

On Competitive Nonlinear Pricing

Many financial markets rely on a discriminatory limit-order book to balance supply and demand. We study these markets in a static model in which uninformed market makers compete in nonlinear tariffs to trade with an informed insider, as in Glosten (1994), Biais, Martimort, and Rochet (2000), and Back and Baruch (2013). We analyze the case where tariffs are unconstrained and the case where tariffs are restricted to be convex. In both cases, we show that pure-strategy equilibrium tariffs must be linear and, moreover, that such equilibria only exist under exceptional circumstances. These results cast doubt on the stability of even well-organized financial markets.

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.