Game Theory for Sumo Wrestling
http://www.nber.org/papers/w7798.pdf
You would think that a combat sport such as sumo wrestling would not be corrupt. The sport has been around for so long, so how could there possibly be a dominant strategy? Within the hierarchy of sumo wrestling a thousand years ago, each wrestler is given a score based on their performance during that season. The higher up on the rankings, the fewer duties they are responsible for. But the system is cut throat. In a 15 match season, you will get promoted if you have more wins than losses (8/7) and demoted if you have more losses than wins(7/8). Relationships between athletes are fairly linear except for the last competition matchups between competitors who are (7/7).
Game theory can be used to analyze this situation. Wrestlers who are (7/7) going into their last match are 70% more likely than expected to win. The dominant strategy for someone who is (7/7) competing against someone else who has 8+ wins is to have the person (7/7) win. That’s because this option favors both players; they will both have more wins then loses. The person who has 8+ wins may also throw the match on purpose because his opponent is a close acquaintance and would not want to see him demoted. All athletes can relate that it is hard training with someone and watch them lose when you have great achievements. This empathy rigs the system of promotion/demotion because there is a strategy both players can choose that allows them each to win. Crazy to think that a sport as old as sumo wrestling can be manipulated in such a way.