The impact of social pressure of differing audience size on referees and team performances from a North American perspective

The COVID-19 pandemic provides a natural experiment to comprehensively test the effect of crowds on both referees and players. Our aim is to examine this from a North-American perspective using data from three major leagues: National Basketball Association (NBA), National Football League (NFL) and National Hockey League (NHL). In all three leagues in the 2020-2021 season, matches were played either under empty or partially loaded stadiums. We find that the audience size for NBA substantially affects referee decisions by increasingly favouring the home team as crowd size grows. No such effect is observed for NHL or NFL. Nonetheless, with increasing crowd size not only for NBA but also for NHL the home team’s performance gets significantly better. Regarding NFL, we have not found evidence that crowd size influences either referee decisions or home team’s performance. We verify that these findings also hold for the pre-COVID-19 pandemic period, when games were normally organized and crowd size only innately varied without any imposed restrictions. These results suggest that the effect of social pressure on the agents’ behaviour is activity specific, no general rules apply. Besides, we claim that out of these three leagues NBA is the most biased in terms of referee decisions.