The home run rate in Major League Baseball spiked dramatically in the second half of the 2015 season and has remained on an upward trajectory every since. As a result, we are on pace to shatter the all-time single season home run record in 2017 by over 300 homers.
Many people have asked why the home run rate has spiked and many potential answers have been offered. Among them are explanations which credit batters who swing harder, with greater uppercut swings, pitchers who throw harder, which could correlate with farther-hit balls when contact is made as well as other factors.
But an obvious explanation is a juiced ball. There is a long and rich history of changes — even slight changes — to baseball composition leading to dramatic increases in offensive levels. The dead ball era ended, in large part, because different wool was used beginning in 1919. The National League changed balls in order to intentionally boost offense in 1930 and it worked almost too well. There was a change of baseball manufacturers in the late 1970s which led to a mini spike. 1987 was the year of the so-called “rabbit ball.” That was never fully explained, but there are strong suspicions that Major League Baseball messed with the ball that year.
Many have looked at the recent surge in home runs and have tried to determine whether the baseball had been juiced. Most notably, Ben Lindbergh of The Ringer and Rob Arthur of FiveThirtyEight studied the matter last year. They concluded that the ball had not been altered. Later Major League Baseball said that its own research showed no changes to the ball, though they did not release their data for outside scrutiny. The mystery remained.
Now, however, they mystery has been solved.
Today Ben Lindbergh writes about the research of baseball analyst and author Mitchel Lichtman (you may know him as MGL). Lichtman obtained several baseballs used in games between 2015 and 2016 and had them tested. The results clearly point to a new ball coming online right around the time the home runs began flying:
The testing revealed significant differences in balls used after the 2015 All-Star break in each of the components that could affect the flight of the ball, in the directions we would have expected based on the massive hike in home run rate. While none of these attributes in isolation could explain the increase in home runs that we saw in the summer of 2015, in combination, they can.
I encourage you to read the entire article, which explains the testing process and the factors which go into ball flight in general. It also contains an important argument about how it’s not wise to look at a single factor in isolation when it comes to studying this stuff. Yes, the ball appears to be different and that difference seems to account for the home run spike, but there are related factors which may have intensified it and perpetuated it separate and apart from the ball itself. It’s a complicated topic — physics always is — so the explanation is necessarily complicated too.
But complicated does not mean unclear. And it seems pretty clear based on this article that the ball was changed, it was changed intentionally and that those changes are the primary reason we are seeing a record number of homers.
Now the ball is the court of Major League Baseball. Care to comment, Mr. Manfred?