What Is the Random Walk Theory?
Random walk theory suggests that changes in stock prices have the same distribution and are independent of each other. It assumes the past movement or trend of a stock price or market cannot be used to predict its future movement. In short, random walk theory proclaims that stocks take a random and unpredictable path that makes all methods of predicting stock prices futile in the long run.
Random walk theory believes it's impossible to outperform the market without assuming additional risk. It considers technical analysis undependable because chartists only buy or sell a security after an established trend has developed. Likewise, the theory finds fundamental analysis undependable due to the often-poor quality of information collected and its ability to be misinterpreted. Critics of the theory contend that stocks do maintain price trends over time – in other words, that it is possible to outperform the market by carefully selecting entry and exit points for investments.
