Following merger, an optimal mechanism discriminates against merging bidders with higher reserve prices and by allocating more often towards non-merging bidders. In this setting, we show that mergers always harm the auctioneer, benefit non-merging bidders, can increase total surplus, and have...

In a private values, open auction, we show that bidder surplus can be expressed as a simple difference between unconditional moments of order statistics. The strength of the result is its simplicity and generality, as we dispense with the typical assumptions of independence and/or symmetry. We...