Publication Date: May 2003
Revision Date: April 2004
The mechanism design literature assumes too much common knowledge of the environment among the players and planner. We relax this assumption by studying implementation on richer type spaces.
We ask when ex post implementation is equivalent to interim (or Bayesian) implementation for all possible type spaces. The equivalence holds in the case of separable environments; examples of separable environments arise (1) when the planner is implementing a social choice function (not correspondence); and (2) in a quasilinear environment with no restrictions on transfers. The equivalence fails in general, including in some quasilinear environments with budget balance.
In private value environments, ex post implementation is equivalent to dominant strategies implementation. The private value versions of our results oﬀer new insights into the relation between dominant strategy implementation and Bayesian implementation.
Mechanism design, Common knowledge, Universal type space, Interim equilibrium, Ex-post Equilibrium, Dominant strategies
JEL Classification Codes: C79, D82
Published in Econometrica (November 2005), 73(6): 1771-1813 [DOI]