Kagan: The challenge of explaining the home run explosion

From SABR member David Kagan at The Hardball Times on October 1, 2019:

Well, it’s autumn. Time to start thinking about cleaning out the vegetable garden…oh, and the postseason, of course! When I planted my tomatoes last spring, I decided to stop spending so much money on the expensive fertilizer I bought in previous years. It was “guaranteed” to increase the size of my fruit. Over the summer, I thought I noticed smaller tomatoes–but then again, how could I really tell? After all, the natural variation in the size of tomatoes was much larger than any decrease in their average size.

This is the essential challenge of explaining the home run explosion over the last couple of years.  As the MLB Report on Home Runs states, “We find that the ball-to-ball variation in the drag and lift coefficients is large compared to the size of changes of average values that would lead to the home run surge.” There is little evidence the ball is coming off the bat faster, nor are there any telltale signs of PEDs. The most likely problem is an (as-yet unexplained) drop in the drag coefficient of the ball.

Since this is likely to be the most home-run-filled postseason ever, it might be time to try to understand why, a year and a half since the report, no one has found the definitive cause for the drop in the drag coefficient on today’s baseballs. (If the words “drag coefficient” start to raise that uncomfortable feeling known as “jargon-terrors,” and you want to start throwing “drag coefficient” around yourself, perhaps “The Physics of the MLB Report on Home Run Rates” will help.)

Read the full article here: https://tht.fangraphs.com/the-challenge-of-explaining-the-home-run-explosion/

Originally published: October 2, 2019. Last Updated: October 2, 2019.