The price fluctuation of assets negotiated in capital and financial markets has been the subject of a theoretical dispute between different methodological streams: some researchers understand that prices are determined at random, based on new information, and that investors decide rationally, according to the principles of efficient market theory. On the other hand, other researchers consider that reality is far more complex, so that no one is able to envisage all variables when investing, and that emotional factors play an important role in investors' decision. The latter support the behavioral finance theory. This article points out the main characteristics of efficient markets and presents some anomalies that are widely discussed among researchers to refute market efficiency.
Market Efficiency; Random Walk; Behavioral Finance; Rationality; Chaos