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A second study confirms that home runs are up due to a change in the baseball

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Two weeks ago Ben Lindbergh and Mitchel Lichtman released their study at The Ringer which convincingly argues that changes in the composition and construction of the baseball is responsible for the dramatic spike in home runs we’ve seen since the middle of the 2015 season. Yesterday their work was corroborated.

Rob Arthur of FiveThirtyEight, who had last year conducted a study with Lindbergh which proved inconclusive on the matter, has revisited the baseballs as well. Specifically, he used baseball’s data with respect the speed of the ball when it is released from a pitcher’s hand and when it crosses the plate and, based on the loss in velocity in that short period, calculated the ball’s drag coefficient. From that he could compare the drag on the ball from before mid-2015 and the drag since mid-2015.

His conclusion: there has been a significant decrease in the drag on baseballs over the past two years and that decreased drag can account for about five feet of carry on a given fly ball. That, in turn, would account for a 10-15% spike in home runs on average, and a bigger spike in any given month depending on other factors. Arthur:

It’s highly unlikely that we’d see that kind of difference by chance without a real change to the ball: The monthly variation in estimated drag coefficients in the past five seasons varied from around 0.34 to 0.355, a far wider range than we’d expect from random variance alone. In total, the practical effect of shifting from a high-drag month to a low-drag month could be around a 30 percent difference in home run rates.

Arthur cautions us not to become conspiracy theorists here. The change in the ball need not be nefarious as even small alterations in the manufacturing process could lead to these changes. At the same time, he reminds us, that we should ignore MLB’s statements that the balls still fall under the league’s manufacturing requirements and performance parameters, because those parameters are quite broad and allow for these significant variations in ball flight. Even if no one is intentionally doing this and even if the balls are officially up to snuff, they can nonetheless have changed significantly and are the likely culprit for the dramatic home run spike.

Stepping back from the research, this makes a lot of sense. As we’ve noted in the past, there is a long and rich history of changes — even slight changes — to baseball composition leading to dramatic increases and decreases 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.

Other factors matter — new parks with shorter porches, batters making a point to swing with an uppercut, diluted pitching, PEDs, etc. — but none are as significant as changes to the ball itself and none account for the almost immediate spike in homers in the middle of the 2015 season.

Anyway, enjoy the dingers. They’re here to stay. Or at least until the baseballs change again.

 

Why Ryan Zimmerman skipped spring training

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All spring training there was at least some mild confusion about Nationals first baseman Ryan Zimmerman. He played in almost no regular big league spring training games, instead, staying on the back fields, playing in simulated and minor league contests. When that usually happens, it’s because a player is rehabbing or even hiding an injury, but the Nats insisted that was not the case with Zimmerman. Not everyone believed it. I, for one, was skeptical.

The skepticism was unwarranted, as Zimmerman answered the bell for Opening Day and has played all season. As Jared Diamond of the Wall Street Journal writes today, it was all by design. He skipped spring training because he doesn’t like it and because he thinks it’ll help him avoid late-season injuries and slowdowns, the likes of which he has suffered over the years.

It’s hard to really judge this now, of course. On the one hand Zimmerman has started really slow this season. What’s more, he has started to show signs of warming up only in the past week, after getting almost as many big league, full-speed plate appearances under his belt as a normal spring training would’ve given him. On the other hand, April is his worst month across his entire 14-year career, so one slow April doesn’t really prove anything and, again, Zimmerman and the Nats will consider this a success if he’s healthy and productive in August and September.

It is sort of a missed opportunity, though. Players hate spring training. They really do. if Zimmerman had made a big deal out of skipping it and came out raking this month, I bet a lot more teams would be amenable to letting a veteran or three take it much more easy next spring. Good ideas can be good ideas even if they don’t produce immediately obvious results, but baseball tends to encourage a copycat culture only when someone can point to a stat line or to standings as justification.

Way to ruin it for everyone, Ryan. 😉