Understanding the Efficient Market Hypothesis
The Efficient Markets Hypothesis (EMH) is a popular school of thought in finance that can be traced back to Eugene Fama. Fama proposed that it is challenging to generate investment returns that continuously exceed the general market average, as shown by major stock indexes like the S&P 500 (CFI, 2022). While a fortunate investor could purchase a stock that earns him enormous short-term gains, according to Fama’s thesis, they might not achieve a return on investment greater than the market average in the long term (CFI, 2022).
The core premise of the EMH theory is the availability of information on companies’ market values (Malkiel, 1989). Since many buyers and sellers are always in the market, prices are constantly and effectively changing. This statement means that equities always reflect their true worth in the market.
Since stocks are constantly exchanged at their actual market value, the primary implication of the theory is that it is challenging to acquire undervalued stocks at a discount or sell overpriced stocks for additional gains. In the long run, skilled stock research and properly executed market timing tactics can only beat the market’s average return. If this is the case, the only option for investors to earn higher returns is to expose themselves to a far higher degree of danger. The theory comes in three distinct variants, each assuming a different degree of market efficiency: the weak, semi-strong, and strong forms.
The Three Levels of Market Efficiency: Weak, Semi-Strong, and Strong
Weak
Securities prices in the weak version of the EMH are assumed to represent all publicly accessible market information. However, this may include something other than recent information. It presumes that historical price, volume, and return data do not predict the future (CFI, 2022). As a result of the inability to extrapolate from previous price performance to anticipate future price movement based on new information, the weak version of the EMH means that technical trading methods cannot offer persistent excess returns (CFI, 2022). Despite its rejection of technical research, the weak form leaves the potential that greater fundamental analysis might help investors get a higher return on their money than the market average.
Semi-Strong
When taken to its semi-strong version, the theory discredits the value of both technical and fundamental assessment. This version builds upon the information from the weak variant. The additional premise is that price is easily affected by updates in public information, which renders forecasts of price movements ineffective (CFI, 2022). In the United States, for instance, the market reacts quickly to fresh information, such as the monthly Non-farm Payroll Report.
Strong
The strong form of the theory suggests that prices reflect all available and unavailable information. All data, both old and new, old and new, and current and up-to-date, are included, as well as any data that has been shared with the public (CFI, 2022). It is generally accepted that a firm’s stock price already reflects all accessible information, even information not readily available to the investing public, such as information known only to the company’s CEO. The strong version of the EMH thus states that no amount of insider information will provide an investor with a prediction advantage significant enough to deliver returns that beat the market average regularly.
Implications of the EMH on Individual Investor Decision-Making
Widespread endorsement of the efficient markets theory has contributed, at least partly, to the meteoric growth in popularity of index funds that follow key market indexes, both among mutual fund investors and those who prefer ETFs. The reason lies in the difficulty of outperforming overall market development. Consequently, investors considering EMH tend to focus on investment in passive index funds that attempt to concentrate on market effectiveness.
References
Corporate Finance Institute (CFI). (2022). Efficient Markets hypothesis. Corporate Finance Institute. Web.
Malkiel, B. G. (1989). Is the stock market efficient? Science, 243(4896), 1313-1318.