Are Pitchers Getting Better than Hitters?

Skip links to an interesting article by Tim Kurkjian at ESPN on the improvement of pitchers in MLB. What caught my eye first was the quote by Jeff Bagwell.

“Pitching is so much better today,” says Astros first baseman Jeff Bagwell. “When I came up (1991), 91 (mph) is about as hard as anyone threw except for like (Rob) Dibble who threw 94. Now, almost everyone throws 94, and most of them are starting pitchers. Look at Juan Cruz (of the Cubs). He throws 97 (mph) and he can’t make their rotation.”

This puzzled me. Was he serious? If you look at the stats there is no doubt that hitters are doing much better than pitchers today when compared to 1991 with these NL stats.

Year – HR/Team – SLG – Ave.
1991 – 119 – .373 – .250
2003 – 169 – .417 – .262

But as Skip points out, Tim K. is not out to defend Bagwell’s grumpy old man syndrome. There is no doubt that pitchers now have less of an advantage over hitters than they did 15 years ago, but the recent offensive surge may be waning. I’m not so sure, and this table explains the reason for my skepticism.

Year	AveERA	C.V.ERA
1990	4.12	0.381
1991	4.21	0.395
1992	4.04	0.392
1993	4.45	0.341
1994	4.87	0.360
1995	4.81	0.396
1996	5.00	0.372
1997	4.89	0.393
1998	4.76	0.395
1999	5.02	0.381
2000	5.16	0.382
2001	4.68	0.368
2002	4.64	0.409
2003	4.72	0.410
		
Mean	4.67	0.38
Median	4.74	0.39
SD	0.344	0.019 

This table lists the average ERA and the Coefficient of Variation of ERA for MLB pitchers facing more than 50 batters in a season. The C.V. ERA is simply the SD/Mean, which superior to simple SD which is biased by the Mean. The C.V. is important because it tells the dispersion of quality among all pitchers in the league. Because athletic performance hits a wall on the right side of the talent distribution, increased dispersion normally means an increase in lower-quality players. More lower-quality pitchers means more opportunities for very good players to take advantage of the bad players. This leads to more records being broken. (If this idea interests you, read Stephen Jay Gould’s “Death of the .400 Hitter.” in Full House.) With dispersion on the rise, I would not be surprised if some very good batters have some career years this year.

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