Resolving Uncertainty about the Number of Bidders in Independent Private-Value Auctions: An Experimental Analysis

Results from first-price, sealed-bid auctions, in which there is uncertainty regarding the number of bidders, are reported. Consistent with recent theoretical findings, concealing information regarding the number of bidders raises more revenue for the seller than revealing information. Individual bids show that (1) narrowly interpreted, the Nash equilibrium bidding theory underlying these theoretical predictions is rejected, as less than 50% of all bids satisfy the strict inequality requirements of the theory, but (2) a majority of the deviations from these inequality requirements favor the revenue-raising predictions of the Nash model, and, in a large number of cases, involve marginal violations of the theory.