Which term refers to the efficiency where prices reflect all past market information such as price and volume?

Weak form efficiency is the concept that states that all past market information, including historical prices and volumes, is already reflected in current stock prices. This form of market efficiency suggests that stock prices move according to new information rather than past information. It implies that technical analysis, which relies on past price movements to predict future price movements, is ineffective because past price data is already incorporated into stock prices.

In the context of this question, weak form efficiency specifically addresses the idea that information about past performance and trends cannot provide an advantage to investors since it is already processed by the market. Therefore, no investor can achieve superior returns simply by analyzing historical data.

This understanding of weak form efficiency plays a crucial role in the broader context of market efficiency theory, which encompasses other forms like semi-strong and strong form efficiency, reflecting different levels of information dissemination and incorporation into asset pricing.