Auction Design without Commitment

We study auction design when parties cannot commit to the mechanism. The seller may change the rules of the game any (finite) number of times and the buyers choose their outside option at all stages. The mechanism is playable in truthful stratgies if the seller can commit to implement the outcomes of the mechanism. A consistency and one-deviation property are defined that characterize the seller’s dynamic mechanism selection problem. The unique consistent mechanism selection rule that meets the one-deviation property and stationarity is English auction.