OWN‐NATIONALITY BIAS: EVIDENCE FROM UEFA CHAMPIONS LEAGUE FOOTBALL REFEREES

We examine the existence and magnitude of own‐nationality bias. Using player‐match level data from 12 seasons of the UEFA Champions League (UCL) and referee assignment policies that pair players and referees from the same country, we determine the bias that referees exhibit toward players from their native country. Players officiated by a referee from the same country receive a 10% increase in beneficial foul calls. Referees' own‐nationality bias is more pronounced for national team players, players at home, and in later stages of the tournament. Elite referees exhibit as much, or more, own‐nationality bias as their less experienced counterparts. (JEL L83, J15)