Between the 2010 and 2011 NFL seasons, in an attempt to reduce injuries and protect the safety of the players, the league moved the placement of kickoffs from the 30-yd line to the 35-yd line. It was thought that advancing the ball would increase touchbacks and reduce high-speed, head-on collisions between players, which are frequent during kickoff returns.

At least in terms of increasing the percentage of touchbacks, the intended effect of the rule change has been realized. During this past off-season, owners voted down a proposal to move the line another five yards to the 40. This almost certainly would have raised the percentage of touchbacks even further.

In an effort to focus only on the location to where the ball was returned, I have excluded kickoffs that were fumbled and recovered by the kicking team. The field position measured is based on the first play by the receiving team after the kickoff. As such, penalties assessed during the kickoff are accounted for, but kickoffs received at the end of a half are not included. There were approximately 2500 kickoffs included per season, so each multi-season graph represents more than 7000 kickoff returns.

Data source: http://www.advancednflstats.com/2010/04/play-by-play-data.html