Prior to the 2013 season, the NFL instituted a new concussion protocol designed to better identify and treat players who may have suffered a head injury during a game. After three seasons, the number of reported concussions is up, but it is still surprisingly low.

During the 2015 season, 317 concussions were reported by NFL teams, according to data from the NFL and data collected by StatNews. That is consistent with the 2013 and 2014 seasons, but way up from the 2012 season when just 173 concussions were reported.

On the surface, hundreds of concussions sounds like a lot. But it works out to an average of just 9.9 concussions per team over the entire season, or less than one per game. Maybe that is how often players suffer concussions, but it feels low.

There is also still a huge disparity in the number reported by individual teams. The Chargers reported 23 concussions this season, the most in the NFL. The Dolphins reported three this year and just 11 in the past four years combined.