An Inefficient Truth

Abstract The Efficient Market Hypothesis often seems to suggest only that most people cannot outguess the financial markets. But the originator of the hypothesis, Eugene Fama, made the stronger claim that people cannot outguess the financial markets because financial-market prices are correct: They incorporate all known information accurately. This view omits the role that human traders’ interpretations of information must play if the information is to prompt them to buy or sell. Buyers and sellers disagree about the meaning of current information, so at least half of them must be wrong. Bringing in many more (but equally fallible) people to predict the future does not somehow make their (collective) answer “right.” This is a logical disproof of the Fama hypothesis, but the inherently speculative nature of financial markets makes its empirical falsification (or verification) ambiguous if not impossible. The hypothesis must therefore be considered an unscientific article of faith.