Sabotage in Tournaments: Evidence from a Natural Experiment
利用2009年柔道世锦赛规则变化这一自然实验，研究发现规则变化导致破坏行为大幅增加，且能力较低的选手更可能使用破坏行为针对能力较高的选手，破坏行为降低了福利。
Summary Many tournaments are plagued by sabotage among competitors. Typically, sabotage is welfare‐reducing, but from an individual's perspective an attractive alternative to exerting positive effort. Yet, given its illegal and often immoral nature, sabotage is typically hidden, making it difficult to assess its extent and its victims. Therefore, we use data from J udo W orld C hampionships, where a rule change in 2009 basically constituted a natural experiment that introduced one costless opportunity for sabotage. In J udo, competitors can break an opponent's attack in an unsportsmanlike manner; these are seen as acts of sabotage. Based on a unique dataset of 1,422 fights, we find that the rule change in 2009 has led to a large increase in the use of sabotage. Moreover, sabotage is more likely to be employed by relatively less qualified individuals, and to be targeted at more qualified ones. From a survey among spectators, we show that sabotage is welfare reducing.