The Designated Hitter Rule and Team Defensive Strategy in Japan's Professional Baseball Leagues

Economists have debated whether and why the designated hitter (DH) rule in North American Major League Baseball led to an increase in hit batsmen. We use data from Japan's professional baseball leagues to reexamine this question. Our empirical analyses of hit batsmen for batters as well as by pitchers reveal that the DH rule resulted in increases in hit batsmen even after effects of team batting performance and pitcher quality are controlled for. We argue that the DH rule prompted changes in managerial defensive strategies, in which pitchers of poorly performing teams are instructed to engage in aggressive pitching.