Month: October 2017

An earlier blogpost reported the award of the Nobel Prize in Economics 2017 to Richard Thaler of the University of Chicago for his work on behavioural economics.

In this video of the Chicago Booth Review, Thaler, a vehement critic of the idea of market efficiency, engages in an interesting discussion with Eugene Fama, another University of Chicago Nobel Prize laureate (2013) and widely regarded as “the father of the efficient-market hypothesis”.

In his previous work, Eugene Fama introduced the model of “efficient capital markets”, i.e. markets that fully reflect all available information (see the paper: “Efficient Capital Markets: A Review of Theory and Empirical Work”). The most common version of this model that is defended today, is the “semi-strong version”, according to which all publicly available information is incorporated in stock prices (but information that is held privately by some investors not necessarily so).

Thaler has spent much of his time writing about how people are not completely rational, an assumption that strongly underpins the efficient-markets hypothesis, for example in his book “Nudge” (together with Cass Sunstein) and in his book “Misbehaving: The Making of Behavioral Economics”.

In the discussion with Fama, Thaler distinguishes two aspects of the efficient-markets hypothesis: “One is whether you can beat the market. The other is whether prices are correct.” On the first aspect, Fama and Thaler are in agreement: generally, even professional mutual fund managers fail to consistently beat the market, after subtracting management costs (Michael Jensen from Harvard University first provided evidence for this hypothesis in this paper).

Fama and Thaler do disagree (and rather strongly) about the second aspect, however. In the video, Fama argues as follows about the efficient-market hypothesis: Continue reading “Are markets efficient? A discussion between Thaler and Fama”