Enos Sarris and Ken Rosenthal from The Athletic report that MLB will be making changes to the baseballs used in the games in attempts to reduce the HR numbers which surged in 2019. The article mentions the following:

“In an effort to center the ball with the specification range for COR and CCOR, Rawlings produced a number of baseballs from late 2019 through early 2020 that loosened the tension of the first wool winding,” the memo from the office of the commissioner reads, explaining that this change had two effects — reducing the weight of the ball by less than one-tenth of an ounce, and also a slight decrease in the bounciness of the ball as measured by the COR and CCOR. 

The changes would likely reduce the amount of homeruns that will take place but by how much? It is unclear as to how drastic the changes would be but the article made a reference to how the Korean Baseball Organization deadened the ball by reducing the ball size by 1 gram and the COR from .01 to .02. which resulted in slugging to go down by 14% and home runs were cut by a third in the league. Hopefully this experimentation does not have such a drastic impact as it did with the KBO.

COR (coefficient of restitution) is basically the bounciness of the baseball, but if you want a more nerdy explanation, here is Washington State University Sport Science Laboratory take on Ball COR. “The coefficient of restitution (or COR) is a measure of the energy that is lost during impact. Balls with higher COR will be more lively in play. While it is close to 0.5 for most balls, it can range from 1 (no energy lost) to 0 (all energy lost).“

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