Rational Participation Revolutionizes Auction Theory

Potential bidders respond to a seller's choice of auction mechanism for a common-value or affiliated-values asset by endogenous decisions whether to incur a participation cost (and observe a private signal), or forego competing. Privately informed participants decide whether to incur a bid-preparation cost and pay an entry fee, or cease competing. Auction rules and information flows are quite general; participation decisions may be simultaneous or sequential. The resulting revenue identity for any auction mechanism implies that optimal auctions are allocatively efficient; a nontrivial reserve price is revenue-inferior for any common-value auction. Characterization of optimal auctions is otherwise contentless, in that any auction that sells without reserve is within the setting of one continuous parameter of an optimal auction; seller's surplus-extracting tools are now substitutes, not complements. Revenue comparisons from the exogenous-bidders literature are upheld in a half-space of parameters, overturned in a half-space. Many econometric studies of auction markets are seen to be flawed in their identifcation of the number of bidders.