Auctions with costly information acquisition

We characterize optimal selling mechanisms in auction environments where bidders must incur a cost to learn their valuations. These mechanisms specify for each period, as a function of the bids in previous periods, which new potential buyers should be asked to bid. In addition, these mechanisms must induce the bidders to acquire information about their valuations and to reveal this information truthfully. Using a generalized Groves principle, we prove a very general “full extraction of the surplus” result: the seller can obtain the same profit as if he had full control over the bidders’ acquisition of information and could have observed directly their valuations once they are informed. We also present appealing implementations of the optimal mechanism in special cases. For helpful comments we thank George Deltas, David Martimort, an anonymous referee, and seminar participants in Mannheim, Rutgers, Tel Aviv, Toulouse, the Society for Economic Design 2002 conference in New York, and the 2003 North American Summer Meetings of the Econometric Society in Evanston, IL. Yossi Spiegel thanks the IIBR for financial assistance and Charles Zheng thanks the NSF for grant SES-0214471.