Going, going, gone. Holding an auction can be an extremely efficient way for a seller to set the price of its products, especially if it does not have much information about how much people may be willing to pay for them. Auctions fascinate economists, especially those who specialize in game theory. They have long been a feature of the sale of art and antiques in the rooms of firms such as Sotheby's and Christie's. But in recent years they have played a growing role in other parts of the economy, ranging from the allocation of government-controlled broadcasting bandwidth to the awarding of work to subcontractors by governments and big firms using competitive tendering, and even more recently the sale of goods over the Internet. An English auction is the most familiar. Bidders compete to offer higher prices and drop out until only one remains. In a Dutch auction, the auctioneer calls out a high price then keeps lowering it until there is a buyer. There are various forms of sealed bid auctions. In a first price sealed bid, each buyer submits a price in a sealed envelope and all bids are opened simultaneously, with the highest offer winning. In a second (or third, fourth, and so on) price sealed bid, the highest bidder wins but pays only the second (third, fourth) highest price bid. An English or Dutch auction will work well for a seller if there is more than one serious bidder, as competition will ensure that the price is set at the level at which it is not worth more to any other bidder but the winner. Indeed, in a competitive auction the successful bidder may end up offering more than what is being auctioned is actually worth. This is known as the winner's curse. Which method will generate the best price for the seller depends on how many bidders take part and how well informed they are. Unfortunately for the seller, this information is not always available before the auction takes place.