Nathan: Fly ball carry and the home run surge

From SABR member Alan Nathan at The Hardball Times on August 24, 2017:

One topic that seems to be consuming the baseball world these days is the surge in home runs in the major leagues, starting approximately midseason in 2015. I won’t attempt to document all the data or all the articles that have searched for reasons for the surge. I do want to refer to two recent articles that address one possible reason for it.

Writing for The Ringer, Ben Lindbergh discussed measurements on the size, weight and seam height of baseballs, and suggested changes in these properties might result in increased distances of fly balls, leading to more home runs. 

Writing for FiveThirtyEight, Rob Arthur tooks this basic idea much further. Using the voluminous amount of pitch-tracking data from both PITCHf/x and Statcast–and specifically by looking at the speed lost when traversing the distance from release to home plate–he suggested the air drag on the baseball has gotten smaller in the past several years, and the reduction in air drag is correlated with the increase in home runs per fly ball.

Both of the recent articles suggest part of the home run surge can be explained by better “carry” (a term I will define more carefully later on) on a fly ball, presumably due to properties of the ball that have changed in such a way as to reduce the air drag. That is the issue I want to focus on here, using a very different analysis technique.

Read the full article here:

Originally published: August 24, 2017. Last Updated: August 24, 2017.