We study a principal--agent model. The parties are symmetrically informed at first; the principal then designs the process by which the agent learns his type and, concurrently, the screening mechanism. Because the agent can opt out of the mechanism ex post, it must leave him with nonnegative...

A seller of an item faces a potential buyer whose valuation of the item depends on two private signals. It is well known that when there are informational externalities and the buyer's private signals arrive all at once, it is impossible to implement an efficient sale. I show that if the buyer's...