Random Walk

Random walk

Theory that stock price changes from day to day are accidental or haphazard; changes are independent of each other and have the same probability distribution. Many believers in the random walk theory believe that it is impossible to outperform the market consistently without taking additional risk.

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Random Walk Theory

An investment philosophy holding that security prices are completely unpredictable, especially in the short term. Random walk theory states that both fundamental analysis and technical analysis are wastes of time, as securities behave randomly. Thus, the theory holds that it is impossible to outperform the market by choosing the "correct" securities; it is only possible to outperform the market by taking on additional risk. Critics of random walk theory contend that empirical evidence shows that security prices do indeed follow particular trends that can be predicted with a fair degree of accuracy. The theory originated in 1973 with the book, A Random Walk Down Wall Street. See also: Efficient markets theory.