What can finance learn from sports betting?

Tobias J. Moskowitz has a recent paper on this question, the results are illuminating:

I use sports betting markets as a laboratory to test behavioral theories of cross-sectional asset pricing anomalies. Two unique features of these markets provide a distinguishing test of behavioral theories: 1) the bets are completely idiosyncratic and therefore not confounded by rational theories; 2) the contracts have a known and short termination date where uncertainty is resolved that allows any mispricing to be detected. Analyzing more than a hundred thousand contracts spanning two decades across four major professional sports (NBA, NFL, MLB, and NHL), I find momentum and value effects that move betting prices from the open to the close of betting, that are then completely reversed by the game outcome. These findings are consistent with delayed overreaction theories of asset pricing. In addition, a novel implication of overreaction uncovered in sports betting markets is shown to also predict momentum and value returns in financial markets. Finally, momentum and value effects in betting markets appear smaller than in financial markets and are not large enough to overcome trading costs, limiting the ability to arbitrage them away.

SSRN and video versions of the paper are here.  The underlying idea here is neat.  The marginal utility of consumption is unlikely to be correlated with the outcomes of sporting events, so we can test some propositions of finance theory without having to worry much about those risk factors.  Lo and behold, a version of momentum results still holds up.  And if you would like an exposition of that approach, do see my earlier dialogue with Cliff Asness.  And here is Cliff on Fama on momentum.