Almost Common Value Auctions: An Experiment

In almost common value auctions one bidder has a higher (private) value for the item than the other bidders. Theory predicts that even a small private value advantage can have an explosive effect in English auctions, with advantaged bidders always winning and sharp decreases in revenue. These predictions fail to materialize for experienced bidders who have learned to avoid the worst effects of the winner's curse. Bidding is better characterized as proportional, with advantaged bidders tending to bid as in a pure common value auction after adding their private value advantage to their estimated value of the item.