study the second-price o er feature of eBay auctions in the case where the
seller has multiple units. The opportunity to make second-chance o ers reduces seller
revenue relative to sequential auctions for some regular environments. If the seller can
commit to making fewer second-chance o ers than she would in equilibrium, then the
second-chance o er feature increases seller revenue. Uncertainty regarding the auction
period hurts the seller. The seller is better o if she can credibly announce when she
is o ering her last unit.