Do Markets Filter Irrationality?

It's tough to defend market rationality these days, but University of Chicago's John List is putting up a good fight. Just published in the The B.E. Journal of Economic Analysis & Policy:

Assumptions of individual rationality and preference stability provide the foundation for a convenient and tractable modeling approach. While both of these assumptions have come under scrutiny in distinct literatures, the two lines of research remain disjointed. This study begins by explicitly linking the two literatures while providing insights into whether market experience mitigates one specific form of individual rationality--consistent preferences. Using field experimental data gathered from more than 800 experimental subjects, we find evidence that the market is a catalyst for this type of rationality. The study then focuses on aggregate market outcomes by examining empirically whether individual rationality of this sort is a prerequisite for market efficiency. Using a complementary field experiment, we gathered data from more than 380 subjects of age 6-18 in multi-lateral bargaining markets at a shopping mall. We find that our chosen market institution is a filter of irrationality: even when markets are populated solely by irrational buyers, aggregate market outcomes converge to the intersection of the supply and demand functions.

And here is an opposing viewpoint from a recent working paper by George M. Korniotis of the Federal Reserve and Alok Kumar of the University of Texas at Austin:

This study investigates whether the adverse effects of investors' behavioral biases extend beyond the domain of financial markets to the broad macro-economy. We focus on the risk sharing (or income smoothing) role of financial markets and demonstrate that risk sharing levels are higher in U.S. states in which investors have higher cognitive abilities and exhibit weaker behavioral biases. Further, states with better risk sharing opportunities achieve higher levels of risk sharing if investors in those states exhibit greater financial sophistication. Among the various determinants of risk sharing, behavioral factors have the strongest effects. The average level of risk sharing in states with unsophisticated investors (= 0.121) is less than half of the average risk sharing level in states with financially sophisticated investors (= 0.308). Collectively, our evidence indicates that the high risk sharing potential of financial markets is not fully realized because the aggregate behavioral biases of individual investors impede state-level risk sharing.