The Designated Hitter Rule in Baseball as a Natural Experiment

All but two professional baseball leagues have adopted the “designated hitter” (DH) rule, which allows a team’s manager to designate a player to bat at the plate and run the bases in place of another player, usually the team’s pitcher. Unlike the team’s other players, the designated hitter does not take the field to play defense. This paper provides a survey of a large literature investigating the DH rule’s effect on the incentives of pitchers to hit batters and on changes in the number of hit batsmen. We also consider whether the DH rule provides a good example of a natural experiment, as some professional baseball leagues were “treated” with the DH rule and others were not treated.