Before comparing stock opinions on financial social media (FSM hereafter) with financial analyst recommendations, it’s essential to understand the concept of market efficiency and how these different sources of information impact the Efficient Market Hypothesis (EMH). Financial markets are generally believed to efficiently reflect available information in security prices. According to Fama (1970), if a market is efficient, information spreads very quickly, if not instantly, and is incorporated into security prices without delay. Consequently, neither technical analysis (the study of past stock price patterns to predict future prices) nor fundamental analysis (the study of financial information to identify mispriced stocks) would enable an investor to achieve abnormal returns greater than those obtained from holding a randomly selected, well-diversified portfolio of securities, ceteris paribus.

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Whisperers Versus Analysts and Implications for Market Efficiency

  • Ying Zhang

摘要

Before comparing stock opinions on financial social media (FSM hereafter) with financial analyst recommendations, it’s essential to understand the concept of market efficiency and how these different sources of information impact the Efficient Market Hypothesis (EMH). Financial markets are generally believed to efficiently reflect available information in security prices. According to Fama (1970), if a market is efficient, information spreads very quickly, if not instantly, and is incorporated into security prices without delay. Consequently, neither technical analysis (the study of past stock price patterns to predict future prices) nor fundamental analysis (the study of financial information to identify mispriced stocks) would enable an investor to achieve abnormal returns greater than those obtained from holding a randomly selected, well-diversified portfolio of securities, ceteris paribus.