網上拍賣的經濟學(上)

　　你也許會認為，如果說有一件事經濟學家應該能告訴你如何去做，那就是在拍賣網站eBay上成功登記拍賣物品。畢竟，拍賣理論家在這行享有盛名;其中一位拍賣理論家蘇珊o阿西(Susan Athey)在今年4月贏得了約翰o貝茨o克拉克(John Bates Clark)經濟學獎章。(克拉克獎章獲得者還有保羅o薩繆爾森(Paul Samuelson)、約瑟夫o斯蒂格利茨(Joseph Stiglitz)和史蒂文o萊維特(Steven Levitt)，比諾貝爾獎(Nobel)獲獎者還要罕見。)

　　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.)

　　然而，盡管拍賣理論已經很發達，但其預測容易受到現實中一些波瀾的影響。比如說，標準經濟學假設人是理性的，這種假設通常是對的：在啤酒價格上漲時，多數人都會少喝一些啤酒。不過，拍賣要求有 "如果他認為她認為我認為他那么認為"的推理鏈條，而這種鏈條往往存在薄弱環節。如果任何出價方有任何理由懷疑其他出價方是不理性的，那么，這些環節就會輕易斷裂。

　　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.

　　另一個理論難題是進入拍賣。多數拍賣理論家假定有固定人數的拍賣方存在，他們全都準備好了要出價。不過，雖然經濟學家可以假設出價方存在，eBay的賣方卻不得不去吸引這些人。

　　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.

　　這不是拍賣理論的一個微小疏忽。為移動電話運營商舉行的大規模 "3G"拍賣背后的經濟學家--保羅o克倫佩雷爾(Paul Klemperer)已經表明，一場拍賣中看似微不足道的特點可能會讓出價方卻步，造成巨大(和災難性的)影響。出于這些和其它原因，明智的拍賣理論家在沒有充分了解整個背景的情況下，會避免預測某個具體的拍賣計劃會有什么效果。

　　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.