Mechanism Design with Weaker Incentive Compatibility Constraints

We study an adverse selection problem, where an agent is able to understate his productivity, but not allowed to overstate it. The solution to this problem is generally different than the solution to the standard problem, where no restriction is made on the statements of the agent. We identify a sufficient condition, that does not depend on the distribution of types, under which these two solutions coincide.Mechanism Design, Incentive Compatibility

On the Optimality of Optimal Income Taxation

The Mirrleesian model of income taxation restricts attention to simple allocation mechanism with no strategic interdependence, i.e., the optimal labor supply of any one individual does not depend on the labor supply of others. It has been argued by Piketty (1993) that this restriction is substantial because more sophisticated mechanisms can reach first-best allocations that are out of reach with simple mechanisms. In this paper, we assess the validity of Piketty’s critique in an independent private values model. As a main result, we show that the optimal sophisticated mechanism is a simple mechanism, or, equivalently, a Mirrleesian income tax system.optimal income taxation, mechanism design

On the optimality of optimal income taxation

The Mirrleesian model of income taxation restricts attention to simple allocation mechanism with no strategic interdependence, i.e., the optimal labor supply of any one individual does not depend on the labor supply of others. It has been argued by Piketty (1993) that this restriction is substantial because more sophisticated mechanisms can reach first-best allocations that are out of reach with simple mechanisms. In this paper, we assess the validity of Piketty's critique in an independent private values model. As a main result, we show that the optimal sophisticated mechanism is a simple mechanism, or, equivalently, a Mirrleesian income tax system.Optimal Income Taxation, Mechanism Design

Ex Post Implementation

We analyze the problem of fully implementing a social choice set in ex post equilibrium. Weidentify an ex post monotonicity condition that is necessary and -- in economic environments -- sufficient for full implementation in ex post equilibrium. We also identify an ex post monotonicityno veto condition that is sufficient. Ex post monotonicity is satisfied in all single crossing environments with strict ex post incentive constraints. In many economically significant environments, ex post implementation can be achieved in the direct mechanism. We show by means of two classic examples that ex post monotonicity does not imply nor is it implied by Maskin monotonicity (necessary and almost sufficient for complete information implementation). The single unit auction with interdependent valuations is shown to satisfy ex post monotonicity but not Maskin monotonicity. Ex post implementation in the direct mechanism is also possible in this case. We describe an example where the Pareto correspondence fails ex post monotonicity but Maskin monotonicity is satisfied.Ex post equilibrium, Implementation, Single crossing, Interdependent values

Dynamic Contracting under Permanent and Transitory Private Information

To understand how firms create and maintain long term relationships with consumers, or how procurement relations evolve over time, it is useful to study a dynamic variant of the classical two-type-buyer contract in mechanism design. It is less trivial and more interesting if the utility determinant (or utility type) is not fixed or completely random, and fair assumptions are that it is either stochastic, or given by a distribution whose parameters are common knowledge. The first approach is that of Battaglini (2005), while the second is pursued in this paper. With two possible types of buyers, the buyer more likely to have a high utility type will receive the first-best allocations, while the other will receive the first best only if he has the high utility type

Robust Mechanism Design: An Introduction

This essay is the introduction for a collection of papers by the two of us on "Robust Mechanism Design" to be published by World Scientific Publishing. The appendix of this essay lists the chapters of the book. The objective of this introductory essay is to provide the reader with an overview of the research agenda pursued in the collected papers. The introduction selectively presents the main results of the papers, and attempts to illustrate many of them in terms of a common and canonical example, the single unit auction with interdependent values. In addition, we include an extended discussion about the role of alternative assumptions about type spaces in our work and the literature, in order to explain the common logic of the informational robustness approach that unifies the work in this volume.Mechanism design, Robust mechanism design, Common knowledge, Universal type space, Interim equilibrium, Ex post equilibrium, Dominant strategies, Rationalizability, Partial implementation, Full implementation, Robust implementation

On the legitimacy of coercion for the nancing of public goods

The literature on public goods has shown that e?cient outcomes are impossible if participation constraints have to be respected. This paper addresses the question whether they should be imposed. It asks under what conditions e?ciency considerations justify that individuals are forced to pay for public goods that they do not value. It is shown that participation constraints are desirable if public goods are provided by a malevolent Leviathan. By contrast, with a Pigouvian planner, e?ciency can be achieved. Finally, the paper studies the delegation of public goods provision to a pro?t-maximizing ?rm. This also makes participation constraints desirable