MLB seeing continued surge in home runs
With a home run on Monday or Tuesday night, Cody Bellinger will enter May with 15 home runs, which would be a record. Currently, Bellinger and Christian Yelich this season have joined Albert Pujols (2006) and Álex Rodríguez (2007) as the only players to hit 14 home runs by the end of April.
Bellinger, however, isn’t the only player surging in home runs. The entire league is. According to Baseball Reference, the league is averaging 1.33 home runs per game, which would be by far a record if the season were to end today. The previous record was set in 2017 at 1.26. Before that, the record was 1.17 in 2000, believed by many to be around the apex of the “steroid era.” The homer rate per game was actually well below 1.00 as recently as 2014 (0.86).
While many factors are contributing to the surge in homers, the most noteworthy is the change in the makeup of the baseball. Separate studies concluded that the ball composition has changed in a meaningful way. In a June 2017 study published at The Ringer, Ben Lindbergh and Mitchel Lichtman concluded that baseballs used after the 2015 All-Star break were different in terms of “bounciness,” as well as lower seam height and circumference. Shortly thereafter, FiveThirtyEight’s Rob Arthur found that newer baseballs have a lower drag coefficient (air resistance). For The Athletic in June last year, Dr. Meredith Wills actually deconstructed baseballs and found that the seams on newer baseballs, compared to those from the 2014 season, are nine percent thicker.
A handful of pitchers have complained about the ball, including members of both the Astros and Dodgers during the 2017 World Series. Marcus Stroman blames the change in baseballs for causing “an epidemic” of blisters for pitchers. Other pitchers, including David Price, Brad Ziegler, Jerry Blevins, and Chris Archer also noticed something materially different about the baseballs.
March and April are typically not homer-friendly months due to lower temperatures and poorer weather. In 2015, March and April saw 592 homers across the league. There were 740 in 2016, 863 in 2017, 912 in 2018, and a whopping 1,101 this year -- and we had two days to go when the stat was last updated. That sounds great if you’re a hitter; not so much if you’re a pitcher.