  It is well-known that home team has an inherent advantage against visiting
teams when playing team sports. One of the most obvious underlying reasons, the
presence of supporting fans has mostly disappeared in major leagues with the
emergence of COVID-19 pandemic. This paper investigates with the help of
historical National Football League (NFL) data, how much effect spectators have
on the game outcome. Our findings reveal that under no allowance of spectators
the home teams' performance is substantially lower than under normal
circumstances, even performing slightly worse than the visiting teams. On the
other hand, when a limited amount of spectators are allowed to the game, the
home teams' performance is no longer significantly different than what we
observe with full stadiums. This suggests that from a psychological point of
view the effect of crowd support is already induced by a fraction of regular
fans.
