你也许会认为，如果说有一件事经济学家应该能告诉你如何去做，那就是在拍卖网站eBay上成功登记拍卖物品。毕竟，拍卖理论家在这行享有盛名;其中一位拍卖理论家苏珊o阿西(Susan Athey)在今年4月赢得了约翰o贝茨o克拉克(John Bates Clark)经济学奖章。(克拉克奖章获得者还有保罗o萨缪尔森(Paul Samuelson)、约瑟夫o斯蒂格利茨(Joseph Stiglitz)和史蒂文o莱维特(Steven Levitt)，比诺贝尔奖(Nobel)获奖者还要罕见。)
You might think that if there's one thing an economist should be able to tell you how to do, it's successfully list an item on the auction website eBay. Auction theorists are, after all, celebrated in the profession; one of them, Susan Athey, won the John Bates Clark medal in April. (Clark medallists, who include Paul Samuelson, Joseph Stiglitz and Steven Levitt, are scarcer than Nobel laureates.)
Yet although the theory of auctions is well-developed, its predictions are sensitive to wrinkles in reality. For example, the standard economic assumption that people are rational is usually a good one: when the price of beer rises, most people drink less beer. But auctions require "if he thinks that she thinks that I think that he thinks" chains of reasoning that tend to have weak links. Those links can easily break if any bidder has any reason to suspect that any other bidder is irrational.
Another theoretical conundrum is entry to the auction. Most auction theorists assume a fixed number of bidders, all poised and ready to bid. But while economists can assume bidders into existence, eBay sellers have to go out and hook them.
This is no minor oversight of auction theory. Paul Klemperer, one of the economists behind the massive "3G" auctions for mobile phone operators, has shown that trivial-seeming features of an auction can have big (and disastrous) effects by repelling bidders. For these reasons and others, wise auction theorists would avoid predicting how a specific auction design will work without knowing much more about the context.