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How Handedness and Age Affect Speed

Following up on my post from last week on triples and steals, I thought it would be interesting to see how those two forms of speed are affected by a player's age and handedness. Based on the advice of commenters, I changed the rates of measurement for each.

For stolen bases, I used the number of steals out of an estimate of steal opportunities: times on base (counting reaches on errors) minus triples and homers. So if a player reached base 100 times and had 2 triples and 8 homers, he'd have 90 steal opportunities.

For triples, I used the number of triples out of all in-play extra-base-hits. (I counted inside-the-park homers as triples for these purposes.) I call this "triple stretch rate." If a player has 18 doubles and 2 triples, his triple stretch rate would be 10% (2 out of 20).

My sample is the 369 hitters (107 left-handed, 193 right-handed, and 69 switch hitters) who have had at least 10 seasons of 150 or more plate appearances in the last 30 seasons (since 1982).


Let's start with the effects of aging. The players' speed seems to peak basically as early as they hit the majors--somewhere between 21 and 24. From there, it's generally a steady decline (as you'd expect), until the late 30s, when there is a bit of a rebound. I'm guessing this is due to the natural thinning caused by age; players who are poorly conditioned tend to have shorter careers, and the ones who are left over by age 38 or so tend to be the ones in better shape.

I talk a bit about the interesting handedness results after the jump.

Let's start with triples, where the effects of handedness are a bit more obvious. Since left-handed batters start out a few feet closer to first base, it makes sense that they would have higher triple rates than righties, and indeed they do--across the board, in fact. Across all ages, lefties averaged a triple stretch rate of 11%, compared to 9% for righties.

What's puzzling, however, is that switch hitters do better than either lefties or righties, with an overall stretch rate of 14%. I'd expect them to rank in between the lefties and righties, since they hit both ways. But from age 22 to age 36, switch hitters stretch more triples than the other groups, and often far more. I have a theory for this, but I'll hold off on that for a bit.

For the stolen bases, the lefties and righties do almost exactly the same, with both averaging a 6% steal rate across all ages. This makes sense, since runners who are already on base have no obvious handedness advantage. However, here again we see the switch hitters coming out notably ahead, with an overall steal rate of 9%. Also, the switch-hitters were successful on a higher portion of their steal attempts: 73% vs. 71% for lefties and 70% for righties. How could all of this be?

I can't say for sure, but my hypothesis is that hitters who are able to successfully switch hit at the major-league level are naturally more athletic than other hitters. Less athletic hitters are going to fail at switch hitting or never even attempt it. If this is the case, then we'd expect switch hitters to be faster and, perhaps, to age more gracefully.

What do you think?