Sabotage in Tournaments: Evidence from a Natural Experiment


Sutter is corresponding author. We thank Gary Charness, Pedro Dal Bo, Catherine Eckel, Bruno Frey, Shachar Kariv, Pedro Rey-Biel, Rupert Sausgruber, Marie-Claire Villeval, as well as participants at the Economic Science Association Meeting in Chicago and seminar participants at Brown University, the universities of Erlangen-Nuremberg and Innsbruck, and the Norwegian School of Economics and Business Administration in Bergen for helpful comments and suggestions. We gratefully acknowledge the help of Brent Cooper and Elisabetta Fratini from the International Judo Federation (IJF) who provided data and further assistance, and of Caroline Bonn who collected the questionnaires at the Judo Grand Prix in Amsterdam. Financial support from the Austrian Science Fund (FWF) through project P22772-G11 is gratefully acknowledged.


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 Judo World Championships, where a rule change in 2009 basically constituted a natural experiment that introduced one costless opportunity for sabotage. In Judo, 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.