Previous research has determined that home field advantage (HFA) is positively related to crowd density. Isolating this effect is a substantial empirical challenge as crowd density is endogenous with home win-likelihood via fan interest. We consider a natural-experimental setting that introduces exogenous crowd-density variation into National Football League (NFL) games. COVID-19 safety protocols allow us to disentangle crowd-presence, crowd-density, and built-environment effects upon HFA. We find strong evidence that crowd presence is a significant, substantial source of HFA, but crowd...Read more
