The EMH, the Financial Crisis and the Behavioral Finance
The Efficient Market Hypothesis (EMH) that was first proposed by Fama (1965, 1970) is the cornerstone of the modern financial economic theory. The EMH argues that the market is efficient and asset price reflects all the relevant information concerned about its return. The genius insight provided by the EMH has changed the way we look at the financial crisis thoroughly. However, the confidence in the EMH is eroded by the recent financial crisis. People can not help to ask: if the market is efficient and the price of assets is always correct as suggested by the EMH, why there exists such a great bubble in the financial market during the recent financial crisis? Apart from that, the EMH has even been criticized as the culprit of the recent financial crisis. (See Nocera, 2009 and Fox, 2009) Actually after the EMH was proposed, many anomalies have been found in the financial market and financial economists have developed many theories in order to explaining these anomalies. Among these the most influential one is the so called behavioral finance, which argues that the complex human behavior plays an important part in determining asset prices. The rest of the essay is arranged as follows. Section 2 explains what the EMH implies and its limitations. Section 3 emphasizes on explaining the usefulness of the EMH in the context of the recent financial crisis. Section 4 focuses on interpreting the behavioral finance. Section 5 concludes the essay. 2. The implications of the EMH
According to Ball (2009), the implication of the EMH can be summarized as follows. The implication of the EMH can be decomposed into two parts. The first insight of the EMH is related to the most profound insights of classical economics, that is, there is no excess profit in a complete market, which is due to the fierce competition in the market. If there exists excess profit in such a market, then the entry of new producers will eventually eliminate it. The second insight is that information is symmetric dissemination, which implies that information can flow freely in the market without cost and time lag. Putting these two parts of insights together, the EMH implies that the market is efficient and asset prices reflect all the relevant information concerned about its return, and that investors can only get commensurate return with the cost of exploiting information due to the competition in the market. According to the EMH, people can only expect to get average return in the stock market and it is impossible to beat the market continuously. Note that it is futile to exploit information in order to get abnormal return does not mean that no one should act to exploit information. As a matter of fact, the EMH is a natural result of the fierce competition in the market---if there is no competition in the market, the market can not be efficient. In other words, asset price can not reach its equilibrium level automatically. Ice-cream producers face fierce competition from other producers in the market and it is impossible for them to get abnormal profit, but it is foolish for ice-cream producers to stop making ice-cream because they will get nothing if they do not work. Fama (1970) classifies the market into three categories: the weak form efficiency, the semi-strong form efficiency and the strong form efficiency. In the weak form efficiency market, asset prices reflect all the historical information, so it is impossible to obtain abnormal return using historical data and technological analysis is useless. In the semi-strong form efficiency market, asset prices reflect all the information that is publicly available, and thus it is impossible to get abnormal return using publicly available information. In the strong form efficiency market, asset prices reflect all the relevant information, including all publicly available information and inside information, so investors can only get...
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