From SABR member Rob Mains at Baseball Prospectus on August 28, 2017:
As you probably know, scoring in baseball hit a nadir in 1968, when teams scored just 3.42 runs per game, the second-fewest in history, barely above the 3.38 average in 1908. In response, MLB lowered the pitching mound and shrunk the strike zone. Scoring rebounded to 4.07 runs per game in 1969 and 4.34 in 1970. But then it began marching downward again, especially in the American League.
By 1972, American League teams were scoring 3.47 runs per game, barely above 1968’s 3.41. So the following winter, American League owners voted to implement the designated hitter rule. American League scoring has never dipped below 4.00 runs per game since the DH began.
In its first years, the DH was dominated by old guys, mostly with bad wheels. In 1973, of the eight DHs with the most plate appearances, seven were 34 or older. As the position evolved, DHs trended younger and more athletic, as great hitters who just weren’t good in the field took over: Hal McRae, Paul Molitor, Edgar Martinez, Frank Thomas, Travis Hafner, David Ortiz. And as good—not just old—sluggers gravitated toward the position, DHs became an offensive force.
Read the full article here: http://www.baseballprospectus.com/article.php?articleid=32616
Originally published: August 28, 2017. Last Updated: August 28, 2017.