[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.

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.

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.