Whenever there are whispers about a livelier ball, MLB is quick to disregard the baseball as a factor. There’s never been an explanation for the sudden rise and just as sudden fall in home runs in 1987. The increase from 1992 to 1993 to 1994 has been attributed to PED use, even though there’s some evidence that the ball could have played a role. The recent sudden increase in home runs was addressed by MLB commissioner Rob Manfred at the All-Star Game and he dismissed PED use and juiced baseballs as factors.
As reported by Jerry Crasnick at ESPN, commissioner Manfred said, “The increase in the number of home runs takes place against a different backdrop. Major League Baseball does 22,000 drug tests a year. The World Anti-Doping Agency says we have one of the best testing programs in the world, let alone in professional sports. Our investigative capacity in the area of performance-enhancing drugs is probably the best in the world. So I’m much less concerned that this is due to [PEDs]. We think it has to do with the way pitchers pitch and the way hitters are being taught to play the game. You’ve seen some unusual developments in terms of home run hitters being up in the lineup to get them more at-bats.”
He also dismissed the theory that changes in the baseball could be the culprit, claiming that MLB has done extensive testing on the baseballs and found no changes. Of course, the next time a commissioner of baseball admits to juicing up the baseball will be the first, so Manfred’s denial must be taken with a grain of salt.
Let’s look closer at what Manfred said about pitchers and hitters. “We think it has to do with the way pitchers pitch and the way hitters are being taught to play the game.” It sounds like he is suggesting that hitters are now swinging for the fences and intentionally trying to hit home runs and are more successful with that approach than they were before. To that, I would ask, why didn’t they think of this sooner? Did hitters suddenly figure out how to hit more home runs?
Somehow, this seems unlikely. If hitters have changed their approach to hit more home runs, wouldn’t we expect more fly balls to be a result of that change in approach? Instead, we find that fly ball percentage (FB%) in 2015 was the lowest we’ve seen since 2002 (which is as far back as batted ball data goes, per Fangraphs). The 2016 season has the third-lowest FB% since 2002. Hitters are not hitting more fly balls. They aren’t hitting more line drives either. They ARE hitting more ground balls. The highest ground ball percentage (GB%) since 2002 came last year. This season’s GB% is the third-highest since 2002.
Think about this. Manfred is suggesting that hitters have changed their approach and this has resulted in more home runs being hit. It would be logical to think that a hitter trying to hit a home run would want to put the ball in the air. The numbers show that hitters have hit fly balls less often over the last two years than in all but one season since 2002 and have hit ground balls more often over the last two years than in all but one season since 2002. I believe this is enough to reject Manfred’s assertion about a change in approach.
There is one batted ball statistic that matches with the increasing number of home runs being hit and that is home runs per fly ball percentage (HR/FB). The yearly HR/FB rate from 2010 to 2014 was 9.4%, 9.7%, 11.3%, 10.5%, and 9.5%. Then came 2015. Let’s look at the monthly HR/FB rate for last year:
10.2%–April ‘15
11.3%–May ‘15
10.6%–June ‘15
11.1%–July ‘15
12.2%–August ‘15
12.3%–September ‘15
And we’ll continue this into the 2016 season:
11.8%–April ‘16
12.8%–May ‘16
13.7%–June ‘16
13.9%–July ’16 (through July 10)
Again, something happened last August that has continued through July of this year. Even though fewer fly balls were being hit, more of those fly balls were flying out of the yard. For the time period in which we have batted ball data, the two seasons with the highest HR/FB rate are 2015 (11.4%) and 2016 (12.9%). I think this is further evidence that the ball could be the culprit.
Next: The Bottom Line