Corruption in Professional Sumo: An Update on the Study of Duggan and Levitt

In the December 2002 issue of the American Economic Review, Mark Duggan and Steven D. Levitt published an article on corruption in professional sumo. In the present paper, we update Duggan and Levitt's study to take into account changes since January 2000. We find strong statistical evidence that corruption is reduced after January 2000 but reappears in the period from 2003 to 2006. In addition, we can show that the non-linearity in the incentive structure disappears from 2000 to 2003 and reappears after 2003. These results confirm the findings of Duggan and Levitt, who suggest that the structure of promotion in rankings gives incentives to the sumo wrestlers to rig matches.