The "weak form" of market efficiency is a financial theory that suggests past stock prices and trading volumes do not provide any advantage in predicting future price movements. According to this theory, all available information from historical data is already reflected in current stock prices, making it impossible to achieve consistent excess returns through technical analysis. In the context of the Efficient Market Hypothesis, the weak form is the first of three levels of market efficiency. The other two forms are the semi-strong form, which incorporates all publicly available information, and the strong form, which includes all information, both public and private.