From a broad point of view, the stock market as a whole is efficient. Considering the fact that millions of investors, both retail and institutional, watch, analyze, and participate in it, the difference between the actual value of a company's stock and the reported price is usually relatively small. It is highly unlikely that a single investor will obtain a valuable piece of information used to make a decision that is not already known to other investors. Therefore, the most likely performance an investor can anticipate in a large market is the overall performance of the market itself.
However, smaller markets have fewer participants, and as a result, the likelihood of relevant pieces of information being over looked by other investors increases, thus causing inefficiencies. Experts generally are able to beat the market by being perceptive enough to recognize the important information and quick enough to act upon it.