Henry Aaron and the Lucas Critique

No, not the Henry Aaron at the Brookings Institution.  I mean what the ten year old Tyler Cowen would have called “the real Henry Aaron.”  Nate Silver writes:

What if Aaron had never hit a home run? What if those 755 round-trippers had fallen for base hits instead? (If we’re trying to isolate the effect of his power, that seems like the fairer way to do it, instead of turning them into popups or something.) Would he still be a Hall of Famer?

If all of his homers had been singles, Aaron would still have his 3,771 hits. Instead of being the second-best home-run hitter of all time, he’d be the third-best singles hitter of all time, after Ty Cobb and Pete Rose. His RBI total would have gone way down; based on the number of runs that Aaron knocked in on home runs and singles throughout his career, I estimate that he’d have 1,232 of them rather than 2,297. But 1,232 isn’t a shabby total; it would rank Aaron 141st all time, in the general vicinity of Derek Jeter, Edgar Martinez and George Sisler. He’d still be a lifetime .305 hitter and have a .374 on-base average.

OK, here is where Lucas comes in.  If Hank Aaron did not carry significant home run potential to the plate, he would have seen a lot more blazing fastballs, pitchers’ “best stuff,” and so on.  Why not challenge the hitter and try to blow it by him if all you are risking is a single up the middle?  As it was, pitchers often threw Aaron a variety of slower curves and off-speed junk, stuff he might grab a piece of with the bat but would have a harder time drilling straight over the fence.

And thus a homer-less version of Aaron probably would have had a harder time making contact at all.  And he certainly would have had many fewer walks.  But yet, with the amazing wrists he had…pitchers were afraid of him.

It is funny how the Lucas critique went from one of the most underrated ideas in economics (pre-Lucas), to one of the most overrated ideas (1980s-early 1990s), and now it is back as one of the most underrated ideas again.  If we vary one policy or one element of a calculation or algorithm, other individuals will respond strategically.

Addendum: Scott Sumner adds comment.


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