Ex post implementation in environments with private goods

We prove by construction that ex post incentive compatible mechanisms exist in a private goods setting with multi-dimensional signals and interdependent values. The mechanism shares features with the generalized Vickrey auction of one-dimensional signal models. The construction implies that for environments with private goods, informational externalities (i.e., interdependent values) are compatible with ex post equilibrium in the presence of multi-dimensional signals.Ex post incentive compatibility, multi-dimensional information, interdependent values

Herd Behavior in Financial Markets

This paper provides an overview of the recent theoretical and empirical research on herd behavior in financial markets. It looks at what precisely is meant by herding, the causes of herd behavior, the success of existing studies in identifying the phenomenon, and the effect that herding has on financial markets. Copyright 2001, International Monetary Fund

Transitive regret

Preferences may arise from regret, i.e., from comparisons with alternatives forgone by the decision maker. We ask whether regret-based behavior is consistent with non-expected utility theories of transitive choice and show that the answer is no. If choices are governed by ex ante regret and rejoicing then non-expected utility preferences must be intransitive.Regret, transitivity, non-expected utility

Rank-Preserving Multidimensional Mechanisms

We show that the mechanism design problem for a monopolist selling multiple heterogeneous objects with ex ante symmetric values for the buyer is equivalent to the mechanism design problem for a monopolist selling identical objects with decreasing marginal values. We apply this equivalence result to (a) give new sufficient conditions under which an optimal mechanism is revenue monotone in both the models; (b) derive new results on optimal deterministic mechanisms in the heterogeneous objects model; and (c) show that a uniform price mechanism is robustly optimal in the identical objects model when the monopolist knows the average of the marginal distributions of the units

Incentive compatibility in multi-unit auctions

We characterize incentive compatibility in multi-unit auctions with multi-dimensional types. An allocation mechanism is incentive compatible if and only if it is nondecreasing in marginal utilities (NDMU). The notion of incentive compatibility we adopt is dominant strategy in private value models and ex post incentive compatibility in models with interdependent values. NDMU is the following requirement: if changing one buyer’s type, while keeping everyone else’s types the same, changes this buyer’s allocation then the new allocation must be relatively more attractive (or relatively less unattractive) to this buyer. We also establish a price characterization of incentive compatible mechanisms