Zimmerman: Aging curves revisited: damn strikeouts

From SABR member Jeff Zimmerman at The Hardball Times on February 12, 2020:

Seven years ago, I found that the PED era was hiding that hitters were peaking earlier. I’ve created various aging curves since that article (including the awardwinning series I did with Bill Petti on pitchers) and never found anything out of place. A few times recently, I’ve been asked to revisit the data since the article is six years old and seems dated. I re-ran the numbers and found some pitching adjustments have changed the strikeout aging factors for both hitters and pitchers and, therefore, the overall curves.

My goal was not to go too in-depth into every possible stat. I didn’t delve into every little detail. Instead, I focused on major trends and, when necessary, dove in a little deeper. I used a total value measurement for both pitchers and hitters. Additionally, I compared strikeout rate, walk rate, batting average on balls-in-play (BABIP), and how hard the ball was hit (ISO for hitters, HR/9 for pitchers). Any changes in how players age would be apparent in these metrics and then investigated further.

For the curves, I used two time intervals, from 2005 to 2012 and from 2012 to 2019. Any time before 2005, the aging curves seemed to defy logic. It was as if the players found a secret elixir to keep them from aging.

Read the full article here: https://tht.fangraphs.com/aging-curves-revisited-damn-strikeouts/

Originally published: February 13, 2020. Last Updated: February 13, 2020.