[The extent to which the observed procedures for selling new issues are efficient is studied. We show that a posted-price mechanism, in conjunction with nonbinding preplay communication and participation restrictions, leads to an allocation of the security (and payment) that maximizes the seller's expected revenue, given the informational constraints imposed by the optimizing incentives of the potential buyers.]

The extent to which the observed procedures for selling new issues are efficient is studied. We show that a posted-price mechanism, in conjunction with nonbinding preplay communication and participation restrictions, leads to an allocation of the security (and payment) that maximizes the seller’s expected revenue, given the informational constraints imposed by the optimizing incentives of the potential buyers.

The authors study the performance of the rational expectations hypothesis in multiperiod experimental markets with multiple assets. They find that the markets are generally inefficient from the point of view of full information aggregation. However, arbitrage relationships hold and it is not possible to detect the informational inefficiency by using some standard tests of market efficiency. These findings suggest that the lack of arbitrage opportunities and the failure of common tests to reject inefficiency are not sufficient to conclude that a market is informationally efficient.

The main result of this paper is that the multiple equilibrium problem in mechanism design can be avoided in private-value models if agents do not use weakly dominated strategies in equilibrium. We show that in such settings, any incentive-compatible allocation rule can be made the unique equilibrium outcome to a mechanism. We derive a general necessary condition for unique implementation that implies that the positive result for private-value models applies with considerably less generality to common-value settings.

We study the problem of implementing social choice correspondences using the concept of undominated Nash equilibrium, i.e. Nash equilibrium in which no one uses a weakly dominated strategy. We show that this mild refinement of Nash equilibrium has a dramatic impact on the set of implementable correspondences. Our main result is that if there are at least three agents in the society, then any correspondence which satisfies the usual no veto power condition is implementable unless some agents are completely indifferent over all possible outcomes. Many common welfare criteria, such as the Pareto correspondence, and several familiar voting rules, such as majority and plurality rules, satisfy our conditions. This possibility result stands in sharp contrast to the more restrictive findings with implementation in either Nash equilibrium or subgame perfect equilibrium. We present several examples to illustrate the difference between undominated Nash implementation and implementation with alternative solution concepts.

In this paper, we analyze the problem of designing incentive compatible mechanisms in pure exchange economic environments when agents have incomplete information. The equilibrium concept employed is Bayesian Nash equilibrium and the notion of implemantation is full implementation, which is stronger than the more commonly employed notion of truthful implementation. An allocation rule is truthfully implementable if there exists a direct mechanism to which truth telling is an equilibrium and which yields the allocation rule as its truthful equilibrium outcome. An allocation rule is fully implementable if there exists mechanism which yields the allocation rule as its unique equilibrium outcome. More generally, a set of allocation rules, or a social choice set, is fully implementable if there exist a mechanism whose equilibrium outcomes coincide with the set. This stronger notion of implemention avoids the well known problems of multiple equilibria which arise in direct revelation games. We develop a condition, termed Bayesian monotonicity, which we show is necessary for full implementation. An incentive compatibility condition is also necessary. We prove that Bayesian monotonicity and a slightly stronger incentive compatibility condition are sufficient for full implementation when there are at least three agents. We present several examples of allocation rules which do and do not satisfy our condition. One example is that of an allocation rule which is fully inplementable by an indirect mechanism, but for which every equivalent direct mechanism has multiple equilibrium outcomes.

We study the performance of the rational expectations hypothesis in multiperiod experimental markets with multiple assets. We find that the markets are generally inefficient from the point of view of full information aggregation. However, arbitrage relationships hold, and it is not possible to detect the informational inefficiency by using some standard tests of market efficiency. These findings suggest that the lack of arbitrage opportunities and the failure of common tests to reject inefficiency are not sufficient to conclude that a market is informationally efficient.

This paper characterizes conditions under which asset returns and consumption are consistent with risk‐averse preferences. It is shown that risk aversion is equivalent to “zero arbitrage” on a transformation of the payoff space. The implicit state prices which are dual to this no‐arbitrage condition can be interpreted as prices of “pure consumption hedges.” This zero‐arbitrage restriction implies the usual restrictions associated with nonsatiation. The analysis holds in both complete and incomplete market settings.

This paper characterizes conditions under which asset returns and consumption are consistent with risk-averse preferences. It is shown that risk aversion is equivalent to “zero arbitrage” on a transformation of the payoff space. The implicit state prices which are dual to this no-arbitrage condition can be interpreted as prices of “pure consumption hedges.” This zero-arbitrage restriction implies the usual restrictions associated with nonsatiation. The analysis holds in both complete and incomplete market settings.