Efficient Market Hypothesis vs. Mass Psychology

The theory of Efficient Market Hypothesis has been the subject of argument for many years. One of the main theories on the other side of the fence has been the influence and effects of Mass Psychology, and it's important role and impact on the markets. Read more about this long standing controversy below:

Efficient Market Hypothesis: True "Villain" of the Financial Crisis?
August 26, 2009

By Robert Folsom

Editor's Note: The following article discusses Robert Prechter's view of the Efficient Market Hypothesis. For more information, download this free 10-page issue of Prechter's Elliott Wave Theorist.

When a maverick idea becomes vindicated, there's a good story to tell. It usually involves a person (or small group of people) who courageously challenge the orthodoxy of the day -- and, over time, the unorthodox yet better idea prevails.

A "good story" of this sort has surfaced during the current financial crisis. A chapter of the story appeared in a recent New York Times article, "Poking Holes in a Theory on Markets." The theory in question is the efficient market hypothesis (EMH), which the article suggested is so hazardous that it "is more or less responsible for the financial crisis." This quote tells you most of what you need to know:

"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."

In case your Latin is rusty, Quod erat demonstrandum means "which was to be demonstrated." Its abbreviation (QED) appears at the conclusion of a mathematical proof. In this case, the massive financial bubbles of recent years are the proof that refutes the efficient market hypothesis, which argues that markets move in a "random walk" and are not patterned.

Similar articles in the financial press have reported the demise of the EMH. Just this week an Economist magazine blog included this bold declaration:

"No one has yet produced a version of the EMH which can be tested and fits the evidence. Thus, the EMH must logically be discarded, as a valid hypothesis must be testable."

QED, indeed -- I agreed years ago that the random walk was implausible. But I didn't come to this view because of behavioral economists, although their work over the past decade has certainly been valuable. Instead, I was persuaded by the work of someone who first challenged the financial orthodoxy more than three decades ago, specifically April 1977. As a young technical analyst at Merrill Lynch in New York, his research circulated among several of Merrill's clients. His name for these studies was the Elliott Wave Theorist: the April '77 study was a detailed analysis of the 1975-76 stock market, which offered this comment on the random walk model:

"If market moves are arbitrary (as the random walk proponents suggest), then internal components would rarely 'make sense' mathematically, and then only by statistically insignificant fluke occurrences. However, there seems to be enough evidence that mass psychology, as recorded in the Dow Jones Industrials, form patterns that are uncannily interrelated....At least this much can be fairly reliably stated as a result of this work: This idea that the market is a 'random walk' is probably false."

Robert Prechter left Merrill soon after; he has published the Elliott Wave Theorist in every month since. Every issue has, in one way or another, "convincingly showed that mass psychology, herd behavior and the like can have an enormous effect on stock prices."

So while there may be a good story to tell about behavioral economists, I trust you see why I believe there is a vastly better one to tell.
The "enormous effect" of "mass psychology" and "herd behavior" is exactly what explains the financial downturn that began in late 2007. Prechter's Elliott Wave Theorist anticipated the crisis and warned subscribers beforehand. Likewise, he alerted them to the bear market rally that began last March.

For more information from Robert Prechter, download a FREE 10-page issue of The Elliott Wave Theorist. It challenges current recovery hype with hard facts, independent analysis, and insightful charts. You'll find out why the worst is NOT over and what you can do to safeguard your financial future.

Robert Folsom is a financial writer and editor for Elliott Wave International. He has covered politics, popular culture, economics and the financial markets for two decades, via print, radio and the Internet. Robert earned his degree in political science from Columbia University in 1985.

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