Arthur/Pavlidis: MLB commission confirms that the baseball has changed

From SABR members Rob Arthur and Harry Pavlidis at Baseball Prospectus on May 24, 2018, with mention of SABR member Alan Nathan:

On July 17, 2015, Mike Trout hit one of the first home runs after the All-Star break. It was a walk-off shot to left-center field off of then-Boston Red Sox closer Koji Uehara, and it began a surge in the number of home runs that would accelerate for the next two seasons. Last September, Alex Gordon capped off that surge by knocking the 5,694th dinger in 2017, setting the all-time record for home runs in a season.

In between Trout and Gordon, observers proposed innumerable explanations for the rising tide in homers, from weather to a league-wide shift in offensive philosophy, most notably through anecdotal improvements made by hitters increasing the launch angle of their batted balls. But after months of investigation, a task force of scientists commissioned by Major League Baseball released their report on Thursday and confirmed that the ball itself is largely responsible for the increased number of home runs. While the results of the study are striking, the exact mechanism of the observed changes is yet to be explained.

The commission, chaired by baseball physicist Alan Nathan, found that air resistance was the dominant factor that changed, driving hundreds of additional home runs in the last three years. The report details the results of dozens of new analyses on data collected by Rawlings, MLB, and scientists on the commission itself.

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Originally published: May 24, 2018. Last Updated: May 24, 2018.