The general implication of stock market efficiency is that markets receive new information
about all aspects that affect stock prices but prices adjust with such speed that investors are
not capable of realizing above‐average trading profits by trading on that information.
Tests of the validity of the EMH have been carried out in most of the stock exchanges all
over the world. A comprehensive review of the literature illustrates that even when one
sort of test (the serial correlation coefficient test, the run test, the variance ratio test, etc.)
rejects the random walk hypothesis, other tests may not. For example, tests may show
monthly prices follow a random walk, but weekly prices or daily prices may not.
Alternatively, the returns on indexes for a very long period may be shown to be
independent whilst the returns on indexes for sub‐period may be dependent. Therefore,
applying a variety of tests to different types of data and comparing the results on the bases
of similar sort of data and test implements will improve the accuracy of the study.
Topics that might be covered in this type of study include tests of the EMH (Weak, Semi
strong or Strong form), stock volatility issues or the implications of behavioral finance.
Example research questions could include:
- Evaluating market efficiency by testing for the random walks in stock prices
- Can technical analysts generate abnormal gains?
- Do actively managed funds outperform the market?
Sample Solution
