“If economists wished to study the horse,” a dismal scientist(① 词源背景：'dismal scien...) once joked, “they wouldn’t go and look at horses. They’d sit in their studies and say to themselves: ‘What would I do if I were a horse?’” But at least horses tend to be spared such attention(免于受到这种关注); finance types are not. And one economic idea is especially liable to get them snorting with impatience and asking whether the person who cites it has been near a trading floor(交易大厅).
“如果经济学家想研究马，”一位阴郁的科学家曾开玩笑说，“他们不会去看马。他们会坐在书房里自言自语：‘如果我是一匹马，我会怎么做？’”但至少马儿们幸免于这种关注；金融圈的人可没这么走运。有一个经济思想特别容易让他们不耐烦地哼鼻子，并询问引用它的人是否去过交易大厅。
This is the efficient-market hypothesis, the formal version of which says that investors, in aggregate(总体上，作为一个整体), perfectly and promptly incorporate new information into asset prices. Those who invoke it can often mean something even stronger: that markets therefore provide the best possible forecasts of fundamentals like corporate earnings. In other words, the price is always right, as it surely would be if it were economists cantering around and making all the decisions.(换句话说，价格永远是正确的，如果让经济学家四处慢跑并做所有决定，情况大概就是如此。)
这就是有效市场假说——其正式版本认为，投资者作为一个整体，完美而迅速地将新信息纳入资产价格中。引用该假说的人往往有更强烈的意味：市场因此提供了对公司盈利等基本面因素的最佳预测。换句话说，价格永远是正确的，如果让经济学家四处慢跑并做所有决定，情况大概就是如此。
Right now this Platonic ideal feels especially remote. Retail traders clamour for meme stocks, whipping up prices just to give short-sellers a thrashing(痛击做空者). Shares in GameStop, an ailing(境况不佳的，病弱的) video-game seller selected for such favour in 2020, are still worth more than 20 times as much as they were then. They have done about as well as Nvidia’s, the biggest beneficiary so far of the artificial-intelligence revolution. Nvidia’s fellow tech giants are racing to issue new stock and sell it to the public—a sure sign that they reckon the bull market is nearing its peak. Yet investors are still happily piling in.
目前，这种柏拉图式的理想显得特别遥远。散户投资者抢购meme股票，哄抬价格只是为了痛击空头。GameStop——这家在2020年被选中受此青睐的病弱游戏零售商——股价仍比当时高出20多倍。它们的表现几乎与英伟达相当，后者是人工智能革命迄今最大的受益者。英伟达的科技巨头同行们正争相发行新股并向公众出售——这是一个确凿的迹象，表明他们认为牛市即将见顶。然而投资者仍在开心地涌入。