Imperfect competition is a meaningful feature for macroeconomic analysis only to the extent that it leads to properties qualitatively different from those obtained under perfect competition. In particular, we have to wonder how imperfect competition per se may found an effective fiscal policy....

This paper presents a survey of some recent results on Bayesian mechanisms. We show that efficient Bayesian mechanisms can "nearly always" be constructed by adding a Groves mechanisms and a Bayesian mechanism whose only aim is to balance the budget. In so doing, we present an interpretation of a...