Joe bought a stock at $57 per share. The price promptly fell to $55. Joe held on to the stock until it again reached $57, and then he sold it once he had eliminated his loss. If other investors do the same to establish a trading pattern, this would contradict ________.

Weak form efficiency is also called the random walk theory states that past volume, price movements and earnings do not affect the price of a stock and can not be used to forecast its future direction. Weak form efficiency states that prices of future securities are random and not determined by past events and that there is no relationship between past information and current market prices.

The principle of weak form efficiency has been contradicted because other investors are making use of Joe's past information to create a trading pattern.