Universal possibility and impossibility results

In a setting of private information, the possibility (impossibility) theorem is said to be valid if a balanced mechanism exists (does not exist) which is ex post efficient and satisfies interim individual rationality. If this validity depends on the support only but not the prior distribution of information itself the universal possibility or impossibility theorem is said to hold. The present paper explores the scope of universal possibility and impossibility theorems for an exogenously given outside option as well as for situations where the outside option is a matter of design. (c) 2005 Elsevier Inc. All rights reserved.