????這種理論就是基于消費的資產定價模型。大多數關于股市運作的理論都是基于這樣一種觀點：投資者會思考得出亞馬遜(Amazon)或蘋果(Apple)值多少錢。總體上，通過買賣股票，市場先生會有一些結論。

????但基于消費的資產定價模型認為，這種方式不管用。事實上，投資者很少會花時間來考慮一家公司的股票是低估、還是高估。大多數投資者的投資決策是基于他們有多少錢，打算什么時候把它們花出去。

????“如果我現在沒有現金流，但未來會有很多，我會在一段時間內很緊張，擔心突然之間我會需要現金，”投資咨詢公司Research Affiliates投資與研究管理團隊主管克里斯?布萊特曼表示。

????紐約大學(New York University)的經濟學教授西德尼?路德維金森一直支持基于消費的理論，1月初他參與撰寫的一份研究報告發現，75%的短期股價變動與投資者的風險偏好變動有關。

????這種理論在解釋近期的科技股拋售時非常管用。第一季度，企業利潤并不比上年同期差多少。但經濟的確放緩了。而且，這可能讓投資個體有點擔心他們擁有多少現金，以及他們是否會早于預期就需要現金。如果你擔心近期可能需要現金，你不太可能投資像特斯拉、Twitter這樣的公司，雖然潛力巨大，但尚未產生利潤或規模利潤。但你可能不會擔心投資伯克希爾-哈撒韋(Berkshire Hathaway)、通用電氣(GE)或沃爾瑪(Walmart)這類藍籌股。

????到4月初，美國經濟開始再度提速。與此同時，科技股反彈。

????諾貝爾獎得主普雷斯科特多少認同這種觀點。他認為，股價的主要驅動因素是稅收政策。如果投資者們認為他們將需要支付更多稅款，他們會減少投資。這不能解釋今年或2008年的科技股下跌，但關鍵是，造成股市恐慌的不只是對股票本身的擔憂。

????對于人們為什么突然之間從華爾街奪路而逃，這似乎是一個很好的答案，至少目前是這樣。（財富中文網）

????譯者：早稻米

????The theory is called the consumption-based asset pricing model. Most theories of how the stock market works are based on the idea that investors sit around thinking about what Amazon or Apple might be worth. Together, by buying and selling stock, Mr. Market comes to some conclusion.

????But the consumption-based asset pricing model says that’s not the way it works at all. Investors, actually, spend very little time thinking about whether a company’s shares are undervalued or overvalued. Instead, most investors make their investment decisions based on how much money they have and when they will spend it.

????“Something that has no cash flows now but a lot in the future, I would be nervous about in a period when all of a sudden I think I am going to need cash,” says Chris Brightman, who leads the research and investment management team at investment advisor Research Affiliates.

????In early January, Sydney Ludvigson, an economics professor at New York University who has been a defender of the consumption-based theories, co-authored a study that found that 75% of short-term stock price movements have to do with changes in investors appetite for risk.

????It turns out the theory does a pretty good job of explaining the recent tech selloff. In the first quarter, corporate profits weren’t any worse than they were last year. But the economy did slow. And that may have made individuals slightly more concerned about how much cash they had, and whether they would need it sooner than they thought. And if you are worried about needing cash soon, you are probably less likely to invest in companies like Tesla and Twitter, which have a lot of potential, but are not yet producing profit, or a lot of it anyway. But you might still not be concerned about investing in Berkshire Hathaway or GE or Walmart .

????By early April, the economy was starting to pick up again. And when it did technology stocks rebounded.

????Nobel Prize-winner Prescott kind of agrees. He thinks the main thing that drives stock prices is tax policy. If investors think they are going to have to pay more in taxes, they will invest less. That doesn’t really explain why tech stocks dropped this year, or in 2008—but the point is, stock market panics are not only driven by a fear of stocks.

????And that seems like a pretty good answer as to why people all of a sudden go running for Wall Street’s exits, at least for now.