We investigate the issue of implementation via individually rational ex-post budget-balanced Bayesian mechanisms. We demonstrate that all social choice rules that generate a nonnegative ex-ante surplus, including ex-post efficient ones, can generically be implemented via such mechanisms for any...

In a class of informed principal problems with common values often used in applications we de…fine a particular mechanism which we call the assured allocation. It is always undominated, i.e. efficient among the different types of the principal. We show it is a perfect Bayesian equilibrium...