Safety regulation in professional football: Empirical evidence of intended and unintended consequences.

In response to increasing public awareness and negative long-term health effects of concussions, the National Football League implemented the "Crown-of-the-Helmet Rule" (CHR). The CHR imposes penalties on players who initiate contact using the top of the helmet. This paper examines the intended effect of this policy and its potential for unintended consequences. We find evidence supporting the intended effect of the policy- a reduction in weekly concussion reports among defensive players by as much as 32% (34% for all head and neck injuries), but also evidence of an increase in weekly lower extremity injury reports for offensive players by as much as 34%.