The MLB hitting explosion: another view

What caused the increase in MLB offense starting in the 1990s? J. C. Bradbury speculated in a recent New York Times article, and I had some comments here.

Now, I find a "Nine" article from 2002, by Benjamin G. Rader and Kenneth J. Winkle, called "Baseball's Great Hitting Barrage of the 1990s." (Subscription required.) There, they note that there was a similar hitting increase in the minor leagues, but it started two years later, in 1995-96 instead of 1993-94. Numbers below are per 100AB:

90-95: 27.4 H, 14.3 R, 2.2 HR
1995 : 27.1 H, 14.1 R, 2.3 HR
1996 : 29.4 H, 15.9 R, 3.0 HR
96-99: 28.0 H, 15.5 R, 3.1 HR

Then, they list several possibilities for the MLB increase, and comment on each.

1. The Ball. The authors call this the "most questionable" of the possible hypotheses, citing Bud Selig's denial, and tests commissioned by MLB that found no difference in the physics of today's balls compared to yesteryear's.

I don't find this as convincing as the authors do.

2. The Bat. According to manufacturers, the authors say, the avaerage bat weight dropped from 33 ounces in 1991 to 31 ounces in 1996. "Whereas earlier in the century, players occaionally went for several weeks, and sometimes for an entire season without breaking a bat, players in the 1990s frequently broke several bats in a week of play."

This hypothesis has the advantage that it can probably be checked, if there are records of which players used which bats when. But even if fully 50% of players changed bats, those players would have to have increased their home run count by 80% to account for the observed 40% increase.

3. Cozier Ballparks. The authors dismiss this one after looking at foul territory, distance to the fences, and fence height. They don't look at runs scored in the parks, which would be a more direct way to the evidence.

4. Dilution of Pitching Talent. The authors correctly point out that expansion would have diluted batting talent at the same time.

5. Muscles. "Although we are unable to offer statistical support ... it seems likely that the increasing strength of the hitters has contributed significantly to the offensive barrage." The authors cite dietary supplements, but note that average player size and weight were "virtually identical" in 1990 and 1998.

6. A New Style of Hitting. The authors argue that the high strike was taken away from pitchers early in the 1990s, and quote a Kirk McCaskill complaint from 1994. They say that it also became unacceptable to throw inside, which again benefitted the hitters, who could stand closer to the plate. And, finally, they argue that with the availability of videotape, coaching was able to improve the performance of hitters much more than the performance of pitchers.

I'm not sure what to make of this one; it's mostly anecdote. And would all these factors have happened suddenly, between 1992 and 1994?

Hat Tip: Baseball Think Factory, which points to a sequel to this study.