A study commissioned by Major League Baseball has determined that changes to the baseball contributed to the rise in the home-run rate, the league announced Thursday.
In August 2017, in response to a recent surge in home runs, MLB empaneled a committed of physicists, statisticians and mathemeticians and other experts to examine the possible impact of the ball itself on the increase in homers.
The committee found that the ball as currently manufactured produces less drag as it flies through the air, allowing it to travel farther.
“The committee concluded that the increase in home run hitting since the 2015 season was due, at least in part, to a change in the aerodynamic properties of the baseball (i.e., reduced drag for given launch conditions, as opposed to a change in launch conditions),” MLB said.
The scientists could not determine, however, exactly how the newer balls produce less drag. The difference could not be attributed to any changes in the manufacturing process or materials at the Costa Rican factory that makes the balls.
The size, weight, seam height and COR (coefficient of restitution—a measure of the ball’s “bounciness”) of the newer balls do not account for home run spike, the study conculuded. One hypothesis for the decrease in drag, which could not be proven, is that “the rubber pill may be more centered within the baseball since 2015 and that the ball may be staying rounder while spinning since the 2015 season.”
Baseball fans and media members have long suspected that the increase in home runs could be due to a change in the baseball itself. Observers also postulate that hitters may have changed their approaches at the plate to hit more fly balls and take advantage of the fact that fly balls are now more likely to be home runs.
In light of the study’s conclusions, MLB says it will adopt several measures to monitor the baseballs, including examining the temperature and humidity of each ballpark’s storage locations and implementing aerodynamic testing of game balls.