Exam 11: The Efficient Market Hypothesis

Correct Answer:

Verified

The weak form of the efficient markets hypothesis (EMH) states that stock prices immediately reflect market data. Market data refers to stock prices and trading volume. Technicians attempt to predict future stock prices based on historic stock price movements. Thus, if the weak form of the EMH holds, the work of the technician is of no value.
The semistrong form of the EMH states that stock prices include all public information. This public information includes market data and all other publicly available information, such as financial statements, and all information reported in the press relevant to the firm. Thus, market information is a subset of all public information. As a result, if the semistrong form of the EMH holds, the weak form must hold also. If the semistrong form holds, then the fundamentalist, who attempts to identify undervalued securities by analyzing public information, is unlikely to do so consistently over time. In fact, the work of the fundamentalist may make the markets even more efficient!
The strong form of the EMH states that all information (public and private) is immediately reflected in stock prices. Public information is a subset of all information, thus if the strong form of the EMH holds, the semistrong form must hold also. The strong form of EMH states that even with inside (legal or illegal) information, one cannot expect to outperform the market consistently over time.
Studies have shown the weak form to hold when transactions costs are considered. Studies have shown the semistrong form to hold in general, although some anomalies have been observed. Studies have shown that some insiders (specialists, major shareholders, major corporate officers) do outperform the market.