Increased HRs in MLB: Summary of Public Investigation

HR totals/rates have increased notably in MLB since the ASG in 2015 to present.


  1. I was doing monthly strike zone/league scoring update articles, so noticed the unexpected run scoring/HR spike at the end of August 2015. Rob Arthur, Jeff Sullivan, and others also looked into this last fall.
  2. All of Brian's slides from his SaberSeminar presentation are now available. Part of his study shows that the average height of called strikes has risen since the ASG in 2015.
  3. Out of interest I looked at the average pitch height (of all pitches, not just called pitches or called strikes) by month, and there is no unusual increase post-ASG in 2015.
  4. Rob showed that more line drives were tracked post-ASG 2015 than pre-ASG, and the newly tracked line drives tended to have slower exit velocities than the average line drive.
  5. Jeff showed that home runs are more evenly distributed among players than ever before, and that average line drive/flyball distances are up in 2016 across all types of hitters:
  6. Here are two graphs that highlight the change in exit velocities seen post All-Star break in 2015: