This is great:
This paper studies how social pressure affects the behavior of soccer referees. We make use of an attractive source of exogenous variation in the number of spectators at matches. Due to recent hooligan violence, the Italian government has implemented a regulation that some soccer teams must temporarily play home matches in empty stadiums. We find that referees punish away players much more harshly and home players much more lightly when the games are played in front of spectators compared to when they are not. We find no evidence for the alternative hypothesis that home and away players are affected differently in these games along a number of different outcomes of players, such as the number of tackles. Our results therefore suggest that referees exhibit home bias caused by social pressure from the spectators.
That’s from Behavior under Social Pressure: Empty Italian Stadiums and Referee Bias by Per Pettersson-Lidbom and Mikael Priks at the University of Stockholm. Given that Italian soccer has suffered severely in recent years over allegations (and more than allegations!) of widespread collusion and Mafia involvement, I am sure that there is more to be told…but how to get the data?