Research Papers

Meredith J. Wills, Contributor, The Athletic

The baseball is the one piece of equipment that is used in every game by every player. Since the 1960s, it has generally been consistent…until now. Recently, we have seen a veritable epidemic of changes to the Major League baseball, breaking records and introducing an unprecedented level of unpredictability. Beginning in the second half of the 2015 season, home run rates began to rise, hitting an all-time high in 2017. After a small correction in 2018, a new ball was introduced in 2019 that produced even more offense, topping the 2017 home run record by 11%. Then, at the start of the 2019 MLB postseason, the ball inexplicably deadened. Three changes in the five seasons is, to say the least, uncharacteristic. Here, I examine baseballs from four time periods—pre-2014, 2016-2018, the 2019 regular season, and the 2019 postseason—and find that each show construction differences.

• 2016-2018: Increased lace thickness
• 2019 regular season:
• Smoother leather
• Flatter seams
• Greater spherical symmetry
• Decreased lace thickness
• 2019 postseason: reintroduction of pre-2019 inventory

In this poster, I offer hypotheses for the sources of these differences and how they may have impacted offense. I also consider what to expect for the 2020 season.