The Effect of Efficiency: Non-Predictability

Market Efficiency

Did you know that there are people paid some pretty big bucks to analyze the stock market? They are trying to predict the next great move! Is it possible? Read the article below to discuss the concept of market efficiency as a class.

What Is Market Efficiency?

By Reem Heakal

When money is put into the stock market, the goal is to generate a return on the capital invested. Many investors try not only to make a profitable return, but also to outperform, or beat, the market.

However, market efficiency - championed in the efficient market hypothesis (EMH) formulated by Eugene Fama in 1970, suggests that at any given time, prices fully reflect all available information on a particular stock and/or market. Fama was awarded the Nobel Memorial Prize in Economic Sciences jointly with Robert Shiller and Lars Peter Hansen in 2013. According to the EMH, no investor has an advantage in predicting a return on a stock price because no one has access to information not already available to everyone else.

The Effect of Efficiency: Non-Predictability
The nature of information does not have to be limited to financial news and research alone; indeed, information about political, economic and social events, combined with how investors perceive such information, whether true or rumored, will be reflected in the stock price. According to the EMH, as prices respond only to information available in the market, and because all market participants are privy to the same information, no one will have the ability to out-profit anyone else.

In efficient markets, prices become not predictable but random, so no investment pattern can be discerned. A planned approach to investment, therefore, cannot be successful.

This "random walk" of prices, commonly spoken about in the EMH school of thought, results in the failure of any investment strategy that aims to beat the market consistently. In fact, the EMH suggests that given the transaction costs involved in portfolio management, it would be more profitable for an investor to put his or her money into an index fund.

Anomalies: The Challenge to Efficiency
In the real world of investment, however, there are obvious arguments against the EMH. There are investors who have beaten the market - Warren Buffett, whose investment strategy focuses on undervalued stocks, made billions and set an example for numerous followers. There are portfolio managers who have better track records than others, and there are investment houses with more renowned research analysis than others. So how can performance be random when people are clearly profiting from and beating the market?

Counter arguments to the EMH state that consistent patterns are present. For example, the January effect is a pattern that shows higher returns tend to be earned in the first month of the year; and the weekend effect is the tendency for stock returns on Monday to be lower than those of the immediately preceding Friday.

Studies in behavioral finance, which look into the effects of investor psychology on stock prices, also reveal that investors are subject to many biases such as confirmation, loss-aversion and overconfidence biases.

Think you know something the rest of us don’t?!

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