  The COVID-19 pandemic forced almost all professional and amateur sports to be
played without attending crowds. Thus, it induced a large-scale natural
experiment on the impact of social pressure on decision making and behavior in
sports fields. Using a data set of 1027 rugby union matches from 11 tournaments
in 10 countries, we find that home teams have won less matches and their points
difference decreased during the pandemics, shedding light on the impact of
crowd attendance on the {\em home advantage} of sports teams.
