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tiny. So tiny, in fact, that it’s best to say that on-deck hitters have virtually no effect on the performance of a batter. It takes a very large difference in the ability of an on-deck hitter to have a tiny impact on the outcome for the batter at the plate. Table 1 shows the magnitude of the impact of the ability of the on-deck hitter on the current batter. A one-hundred-point increase in the OPS of the on-deck batter lowers the probability that the current batter will walk by 2.6 percent, get a hit by 1 percent, get an extra-base hit by 3.7 percent, and hit a home run by 3 percent. 13 Even with this rather large difference in on-deck hitter ability, the impact is very small.
    Although protection is a regular topic of concern in the banter of sports commentators, it turns out that it’s not something to worry about at all. Protection is a myth. While pitchers do seem to fear walking batters when there is a good hitter on deck, the benefits of seeing more pitches in the strike zone are offset by greater pitcher effort. Sports announcers have more important things to worry about than protection.

3
    The Extinct Left-Handed Catcher
    left-hand.ed (l 2 ft′h a n′d i d), adj. 4. Of doubtful sincerity; dubious: left-handed flattery; a left-handed compliment.
    —THE AMERICAN HERITAGE DICTIONARY OF THE ENGLISH LANGUAGE, FOURTH EDITION
    CATCHERS TYPICALLY have two qualities: good arms and bad legs. Adam LaRoche ought to be a perfect fit. As the son of former big-league pitcher Dave LaRoche, he has a cannon for an arm. Many teams wanted to draft him as a pitcher, but he wanted to hit. And no one would describe him as speedy. He broke into the majors with the Atlanta Braves in 2004 and has shown the potential with the bat to be a good-hitting catcher. Instead, he toils at first base—a position typically manned by hitters much better than Adam—which makes him seem very ordinary. Why? Because Adam is a victim of discrimination: he’s left-handed, and left-handers don’t play catcher in baseball.
    Benny Distefano is a player whom you might know only as the answer to the trivia question: “Who was the last left-hander to play catcher in the major leagues?” In 1989 Distefano played three games at catcher for the Pittsburgh Pirates, becoming only the fourth southpaw to step behind the plate since the AL and NL merged. The fact that the catcher is a right-handed position has always puzzled me. There seems to be very little gained from excluding one class of players from a sport that generally favors left-handedness. But, as an economist, I’m a big believer in persistence signaling the superiority of a practice. As Nobel Prize–winning economist George Stigler wrote:
    Mistakes are indeed made by the best of men and the best of nations, but after a century are we not entitled to question whether these “mistakes” produce only unintended results? Alternatively stated, a theory that says that a large set of persistent policies are mistaken is profoundly anti-intellectual unless it is joined with a theory of mistakes. It is the most vacuous of “explanatory” principles to dismiss inexplicable phenomena as mistakes—everything under the sun, or above the sun, can be disposed of with this label, without yielding an atom of understanding. 14
    In answering this puzzle, it’s clear that I should heed Stigler’s advice. The strict use of right-handers at catcher is not the result of some whim or official policy of Major League Baseball. It’s a practice that has existed for nearly a hundred years. There has been too much time and too much incentive for teams to discontinue an inferior practice for this to be some sort of historical accident in the guise of traditional wisdom. In this chapter, I reveal what is desirable about limiting catching duties to right-handers, which causes this practice to persist.

The Role of Handedness in Baseball
    The handedness of a baseball player matters on the field, and we tend to think it