This paper studies the design of ex ante efficient mechanisms in situations where a single object is for sale, and agents have positively interdependent values and can covertly acquire information at some cost before participating in a mechanism. We find that when the strength of...

An intermediary must make a decision on behalf of a group of agents, who are privately informed about their valuations attached to decisions. Examples include the government acting as an intermediary in the provision of public goods. We show that an imperfectly informed intermediary can help...