The idea of an efficient market is very important to the study of security analysis and portfolio management. If information is fully reflected in security prices, the market is efficient and it is not worthwhile to pay for information that is already impounded in security prices. The evidence seems to indicate that markets are efficient with respect to most types of information. However, there appears to be certain types of information associated with irregularities in the financial markets. Such irregularities are call market anomalies. Three of the most heavily researched anomalies are the P/E effect, the size effect and the January effect.