Implications and Limitations of the Efficient Market Hypothesis

Late 2000s financial crisis

The financial crisis of 2007–2012 has led to renewed scrutiny and criticism of the hypothesis. Market strategist Jeremy Grantham has stated flatly that the EMH is responsible for the current financial crisis, claiming that belief in the hypothesis caused financial leaders to have a "chronic underestimation of the dangers of asset bubbles breaking". Noted financial journalist Roger Lowenstein blasted the theory, declaring "the upside of the current Great Recession is that it could drive a stake through the heart of the academic nostrum known as the Efficient-Market Hypothesis". Former Federal Reserve chairman Paul Volcker chimed in, saying, "[it is] clear that among the causes of the recent financial crisis was an unjustified faith in rational expectations and market efficiencies".


2008 Financial Crisis
The strong form of EMH is diminished by the 2008 crisis


The financial crisis has led Richard Posner, a prominent judge, University of Chicago law professor, and innovator in the field of Law and Economics, to back away from the hypothesis and express some degree of belief in Keynesian economics. Posner accused some of his Chicago School colleagues of being "asleep at the switch," claiming that "the movement to deregulate the financial industry went too far by exaggerating the resilience - the self healing powers - of laissez-faire capitalism". Others, such as Fama himself, said that the hypothesis held up well during the crisis and that the markets were a casualty of the recession, not the cause of it. Despite this, Fama has conceded that "poorly informed investors could theoretically lead the market astray" and that stock prices could become "somewhat irrational" as a result.

Critics have suggested that financial institutions and corporations have been able to decrease the efficiency of financial markets by creating private information and reducing the accuracy of conventional disclosures, and by developing new and complex products which are challenging for most market participants to evaluate and correctly price.