The efficient market hypothesis (EMH) posits that securities or assets in a market are fairly priced, reflecting all known information that could impact their value. An efficient capital market is best defined as a market in which security prices reflect all available and relevant information. In other words, it is a market where the prices of securities accurately reflect their intrinsic value.
Market efficiency refers to the degree to which market prices reflect all available, relevant information. If markets are efficient, then all information is rapidly and accurately incorporated into security prices, leaving no room for investors to consistently earn abnormal returns. Efficient market theory suggests that investors cannot consistently outperform the market by using past information or any other publicly available information.
In 1970, in “Efficient Capital Markets: a Review of Theory and Empirical Work,” Eugene F. Fama defined a market to be “informationally efficient” if prices rapidly and accurately reflect all available information. This means that any new information relevant to the securities is immediately reflected in their prices, leaving no room for arbitrage opportunities.
The efficient market hypothesis argues that current stock prices reflect all existing available information, making them fairly valued as a result. This implies that it is impossible for investors to consistently generate excess returns by trading on publicly available information. It suggests that securities are always accurately priced and that any attempt to outperform the market is a matter of luck rather than skill.
Market failure, on the other hand, refers to an inefficient distribution of goods and services in the market. In this situation, market prices do not accurately reflect the true value of the securities or assets. Market failures can occur due to various factors, such as information asymmetry, externalities, or monopolistic power. Efficient capital markets aim to mitigate market failures by ensuring that prices accurately reflect all available information.
The Efficient Market Hypothesis (EMH) is an investment theory stating that share prices reflect all information and consistent alpha generation is impossible. It suggests that investors cannot consistently outperform the market by using any publicly available information. This theory has been subject to extensive research and debate within the financial community.
The efficient market hypothesis theorizes that the market is generally efficient but offers three forms of market efficiency: weak, semi-strong, and strong. Weak-form efficiency states that stock prices already reflect all past trading information, making it impossible to predict future prices based on historical data. Semi-strong-form efficiency suggests that stock prices reflect all publicly available information, including news and financial statements. Strong-form efficiency contends that stock prices reflect all information, including both public and private information.
In 1970, Eugene F. Fama, the 2013 Nobel Prize winner, defined a market to be "informationally efficient" if prices always incorporate all available information. This definition underscores the importance of incorporating all relevant information into security prices to ensure an efficient capital market.
While an efficient capital market is desirable, it is important to note that market inefficiencies can still occur, leading to anomalies and temporary deviations from fair value. One such phenomenon is the January Effect, which refers to the tendency for stock prices to rise in the first month of the year following a year-end sell-off for tax purposes. This Effect suggests that there might be seasonal patterns in stock prices that temporarily deviate from their intrinsic value.
In conclusion, an efficient capital market is one where security prices accurately reflect all available and relevant information. It ensures that investors cannot consistently outperform the market using publicly available information. While market inefficiencies may exist temporarily, the overall goal is to maintain an informationally efficient market that minimizes market failures and ensures fair pricing of securities.
