財務會計理論sccot第四章有效證券市場-文庫吧資料
2025-01-12 21:29本頁面
【正文】 here, at any point in time, actual prices of individual securities already reflect the effects of information based both on events that have already occurred and on events which, as of now, the market expects to take place in the future. ?In other words, in an efficient market at any point in time the actual price of a security will be a good estimate of its intrinsic value. History ? Prior to the 1950’s it was generally believed that the use of fundamental or technical approaches could “beat the market” (though technical analysis has always been seen as something akin to voodoo). ? In the 1950’s and 1960’s studies began to provide evidence against this view. ? In particular, researchers found that stock price changes (not prices themselves) followed a “random walk.” ? They also found that stock prices reacted to new information almost instantly, not gradually as had been believed. The Efficient Markets Hypothesis ? The Efficient Markets Hypothesis (EMH) is made up of three progressively stronger forms: ?Weak Form ?Semistrong Form ?Strong Form The EMH Graphically ? In this diagram, the circles represent the amount of information that each form of the EMH includes. ? Note that the weak form covers the least amount of information, and the strong form covers all information. ? Also note that each successive form includes the previous ones. Str ong Form Semi Str ong Wea k Form All historical prices and returns All public information All information, public and private The Weak Form ? The weak form of the EMH says that past prices, volume, and other market statistics provide no information that can be used to predict future prices. ? If stock price changes are random, then past prices cannot be used to forecast future prices. ? Price changes should be random because it is information that drives these changes, and information arrives randomly. ? Prices should change very quickly and to the correct level when new information ar
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