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Vol. 64, No. 2, pp. 132-146 (2013)

“Match-Rigging in Professional Sumo —Elucidation of Incentive Structures and Empirical Analysis—”
Masahiro Hori (Institute of Economic Research, Hitotsubashi University), Koichiro Iwamoto (Department of Contemporary Management, Aichi Gakusen University)

This paper first develops a simple model to show that incentives for match-rigging in professional sumo differ depending on the rank to which a wrestler belongs. While incentives for match-rigging can arise for wrestlers in the top divisions (sekitori), few incentives arise for wrestlers-in-training (makushita and below). We then report the results of our empirical analysis, which show that match-rigging in the top divisions has declined in the post-Duggan and Levitt (2002) period, and that at the wrestler-in-training level there was no statistically detectable match-rigging during any period. We find further that match-rigging in professional sumo has stabilized at statistically undetectable levels following the mobile phone text message match-rigging scandal, and that on average the wrestlers selected for sanctions following the scandal were in fact those most involved in match-rigging.