There are two efficient market hypotheses. One is the bold, unsubstantiated proposition that financial markets are close to perfect and all-knowing. This theory was ferociously and convincingly attacked by Robert Shiller and Lawrence Summers three decades ago and quietly abandoned by its progenitors in the 1990s – although it lived on zombie-style in textbooks, central bank policy and some parts of the financial press until recently. When, these days, a pundit or government official rails against “efficient market theory”, this is what they mean.
有效市場假說有兩種：一種是大膽且未經證實的觀點，認為金融市場近乎完美且無所不知。30年前，這種理論受到了羅伯特?希勒(Robert Shiller)和勞倫斯?薩默斯(Lawrence Summers)猛烈但令人信服的抨擊。上世紀90年代，其創始人悄然放棄了這一理論——盡管直到最近，它還會在一些教科書、央行政策以及部分財經報道中借尸還魂。目前，當一位學者或政府官員指責“有效市場理論”時，他們指的就是這種假說。