Final answer:
The market is said to be weak-form efficient.
Step-by-step explanation:
When investors are not capable of making superior investment decisions on a continual basis based on past prices, public or private information, the market is said to be weak-form efficient.
Weak-form efficiency is one of the three forms of market efficiency, along with semi-strong form efficiency and strong-form efficiency. In weak-form efficient markets, all past price information is already reflected in the current market prices, making it impossible for investors to consistently achieve above-average returns by analyzing historical price data alone.
For example, if the stock market is weak-form efficient, it means that studying a company's historical stock prices will not give an investor an edge in predicting future stock price movements.