The possibility of resale after an auction attracts speculators (i.e., bidders who have no use value for the objects on sale). In a multi-object auction, a high-value bidder may strictly prefer to let a speculator win some of the objects and then buy in the resale market, in order to keep the auction price low for the objects she wins in the auction. Therefore, although speculators increase competition in the auction, they also affect high-value bidders.incentives to .reduce demand..We show that the net e¤ect on the seller.s revenue of allowing resale to attract speculators depends on the heterogeneity of bidders.valuations. But the presence of speculators may increase the seller.s revenue only if speculators are eventually outbid. We also analyze the effect on the seller.s revenue of allowing resale in the absence of speculators, and we discuss the strategies that the seller can adopt to increase his revenue.
