I would post this in the comments to the previous post, but I don’t think I can put images in the comments. There are lots of good comments there, too. A few posters implied—or maybe I’m misinterpreting—that if the best hitters dominated the worst pitchers, shouldn’t the best pitchers dominate the worst hitters too? Well, in fact, pitchers also improved in striking out batters just as they were giving up more home runs and hitting more batters. But, the effect of dispersion has been greater on pitchers than hitters, which should lead to more great feats by hitters.
Also, Skip notes that “HR rates vs. pitchers should diverge in the 90s: the best pitchers dish out fewer, and the worst dish out more.” So, I looked at the divergence of home runs allowed across pitchers, using the coefficient of variation as the measure of dispersion.
Now some of this has to do with the increased specialization of pitchers, which might also be a function of a depleted talent pool, so I also looked at the dispersion of home run rates. The outcome is not as pronounced, and the change in dispersion since the 1993 expansion has been quadratic—decreasing then increasing. And. in a historical context, the dispersion in home runs allowed rates is low.