Home Run Totals Are Up, and It's Because the Ball Is Juiced

The Ringer‘s Ben Lindbergh published an article alongside former MLB consultant Mitchel Lichtman today with findings that suggest the massive increase in home runs since the 2015 season is partially due to changes in the balls construction.

For those that are unfamiliar, league-wide home run totals have spiked since 2015. In 2014, there were 0.86 HRs per game; then 1.01 in 2015, and 1.16 per game in 2016, which is only topped by 1.17 in 2000, the height of the steroid era. This season, we’ve already seen a total of 2,394 home runs, putting the league on pace to break the all-time single season record of 5,693, set in 2000, by almost 350 dingers.

Writers, pundits, statisticians and the like have spent countless hours trying to explain this phenomenon, leaving us with more questions with answers. Many of the obvious explanations have been dismissed, from higher temperatures and widespread PED (performance enhancing drugs) use, to pitchers throwing harder and optimized batting orders. With the above in mind, The Ringer returned to the theory that a “juice ball” is the cause, despite MLB officials claiming that the ball hasn’t changed.

Lichtman commissioned his own independent ball-testing experiment with help from the Sports Science Lab at Washington State University, comparing “coefficient of restitution, or COR — basically, its bounciness,” circumferences and seam-heights on game-used balls from 2014, 2015 and 2016.

Here’s what was said of their findings:

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.

The newer balls have higher CORs and lower circumferences and seam heights, which would be estimated to add an average of 7.1 feet to their distance, equivalent to the effect we would expect to stem from a 1.43 mph difference in exit speed. Although those differences don’t sound enormous, Nathan has noted that “a tiny change in exit speed can lead to much larger changes in the number of home runs.”

In reference to the seam height and circumference of the balls, The Ringer received a quote from FiveThirtyEight writer, Rob Arthur, who is conducting similar research.

“An analysis by Arthur that will be published this week at FiveThirtyEight does show that even after accounting for exit velocity and launch angle, balls hit in the first half of 2016 produced a higher home-run-per-fly-ball rate than balls hit in the first half of 2015, which supports the suspicion that the 2016 balls carried farther. “Balls hit with the same exit velocities and launch angles were much more likely to become home runs in 2016 than in 2015, suggesting that their air resistance might have decreased,” Arthur told us via email.”

Lindergh and Lichtman’s report is much more analytical and stat-driven than the excerpts we chose to include, so please check out their excellent exposé for an in-depth breakdown.

The article concludes however with the notion that the spike in homers being a result of “one contributing cause, so the single smoking gun that addresses every issue is probably a pipe dream.”

We know that some hitters in recent seasons have intentionally tried to hit more balls in the air, and several of them have made themselves much more dangerous at the plate. The idea of elevating the ball isn’t new, but in the past year or two it seems to have made major headway in combating the common belief that it’s better to hit down on the ball. That could be because hitters are trying to avoid increasingly common infield shifts, or it could be because Statcast has made it easier to identify hitters who could benefit from lifting their launch angles.

At the end of the day, more home runs, as well as strikeouts, which are also up, sells more tickets, and arguably makes the game more exciting.