Efficient Market Hypothesis

Efficient Market Hypothesis

States that all relevant information is fully and immediately reflected in a security's market price, thereby assuming that an investor will obtain an equilibrium rate of return. In other words, an investor should not expect to earn an abnormal return (above the market return) through either technical analysis or fundamental analysis. Three forms of efficient market hypothesis exist: weak form (stock prices reflect all past information in prices), semistrong form (stock prices reflect all past and current publicly available information), and strong form (stock prices reflect all relevant information, including information not yet disclosed to the general public, such as insider information).

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Efficient Market Hypothesis

A controversial model on how markets work. It states that the market efficiently deals with all information on a given security and reflects it in the price immediately. The model holds that technical analysis, fundamental analysis, and any speculative investing based on those methods are useless. The model has three forms: weak efficiency, which holds that technical analysis is ineffective, semi-strong efficiency, which holds that fundamental analysis is ineffective, and strong efficiency, which states that even insider information is immediately reflected in the security prices. Investors and academics disagree on how well the model works.