Having spent many years debating my economist friends from the University of Chicago, this article gives a nice overview of the problems with one of the dominant economic theories of our time--efficient market hypothesis. I hope you enjoy and I look forward to any responses.For some months now, Jeremy Grantham, a respected market strategist with GMO, an institutional asset management company, has been railing about — of all things — the efficient market hypothesis.
You know what the efficient market hypothesis is, don’t you? It’s a theory that grew out of the University of Chicago’s finance department, and long held sway in academic circles, that the stock market can’t be beaten on any consistent basis because all available information is already built into stock prices. The stock market, in other words, is rational.
In the last decade, the efficient market hypothesis, which had been near dogma since the early 1970s, has taken some serious body blows. First came the rise of the behavioral economists, like Richard H. Thaler at the University of Chicago and Robert J. Shiller at Yale, who convincingly showed that mass psychology, herd behavior and the like can have an enormous effect on stock prices — meaning that perhaps the market isn’t quite so efficient after all. Then came a bit more tangible proof: the dot-com bubble, quickly followed by the housing bubble. Quod erat demonstrandum.
These days, you would be hard-pressed to find anybody, even on the University of Chicago campus, who would claim that the market is perfectly efficient. Yet Mr. Grantham, who was a critic of the efficient market hypothesis long before such criticism was in vogue, has hardly been mollified by its decline. In his view, it did a lot of damage in its heyday — damage that we’re still dealing with. How much damage? In Mr. Grantham’s view, the efficient market hypothesis is more or less directly responsible for the financial crisis. (more)
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