The Revelation Principle for Mechanism Design with Signaling Costs

The revelation principle is a key tool in mechanism design. It allows the designer to restrict attention to truthful mechanisms, greatly facilitating analysis. This is also borne out algorithmically, allowing certain computational problems in mechanism design to be solved in polynomial time. Unfortunately, when not every type can misreport every other type (the partial verification model) or—more generally—misreporting can be costly, the revelation principle can fail to hold. This also leads to NP-hardness results. The primary contribution of this article consists of characterizations of conditions under which the revelation principle still holds when reporting can be costly. (These are generalizations of conditions given earlier for the partial verification case [11, 21].) Furthermore, our results extend to cases where, instead of reporting types directly, agents send signals that do not directly correspond to types. In this case, we obtain conditions for when the mechanism designer can restrict attention to a given (but arbitrary) mapping from types to signals without loss of generality.

The Revelation Principle in Multistage Games

The communication revelation principle (RP) of mechanism design states that any outcome that can be implemented using any communication system can also be implemented by an incentive-compatible direct mechanism. In multistage games, we show that in general the communication RP fails for the solution concept of sequential equilibrium (SE). However, it holds in important classes of games, including single-agent games, games with pure adverse selection, games with pure moral hazard, and a class of social learning games. For general multistage games, we establish that an outcome is implementable in SE if and only if it is implementable in a canonical Nash equilibrium in which players never take codominated actions. We also prove that the communication RP holds for the more permissive solution concept of conditional probability perfect Bayesian equilibrium.

The revelation principle and mechanism design

This chapter evaluates a more general attack on optimal contract and mechanism design stressing cases of adverse selection, which makes use of the revelation principle. One should be clear about the uses to which the revelation principle is put. It can be thought of as a statement about how actually to implement contracts. But it may be better to use it with greater circumspection as a tool of analysis for finding the limits of what outcomes can be implemented, without reference to how best to implement a particular outcome. In some contexts of direct revelation, there will be situations ex post where the party in the role of the government knows that it can obtain further gains from trade from one or more of the parties who participated. Meanwhile, in many applications of the revelation principle, the party in the role of mechanism designer must be able to commit credibly to no subsequent (re)negotiation once it learns the types of the parties with which it is dealing.

Disclosure to a Psychological Audience

We study how a benevolent expert should disclose information to an agent with psychological concerns. We first provide a method to compute an optimal information policy for many psychological traits. The method suggests, for instance, that an agent suffering from temptation à la Gul and Pesendorfer (2001) should not know what he is missing, thereby explaining observed biases as an optimal reaction to costly self-control. We also show that simply recommending actions is optimal when the agent is intrinsically averse to information but has instrumental uses for it. This result, which circumvents the failure of the Revelation Principle in psychological environments, simplifies disclosure and informs the debate regarding mandated disclosure. (JEL D11, D82, D83, D91)