But is it the ball?

In my previous post about the increase in homeruns since 1993 I listed a number of factors I thought were all contributors including greater strength by hitters, the development of thin handled bats, the use of aluminum bats, and the crackdown on bean balls accompanied by the decreased fear by hitters to lung over the outside corner and drive the ball. In a subsequent post I attempted to quantify the impact of decreased foul territory on homeruns and came to the conclusion that while it has certainly had an effect, the effect is trivial.

There is one other factor that always gets bandied about in such conversations and that is the theory that the ball has been juiced. In many cases this argument is presented with conspiratorial overtones that the powers behind MLB are regularly manipulating the ball to increase offense and thus fan interest. On the SABR list this week Alan M. Nathan, a physicist at the University of Illinois offered that he and a colleague had tested the COR (coefficient of restitution, a measure of the "bounciness" of the ball) of twelve 2004 MLB balls from Rawlings and nine unused mid-1970s baseballs he received from late A's owner Charlie Finley's wife.

His conclusion from this small sample was that the balls were identical to the precision of the measurements. Similar studies I've heard about in the past but can't find at the moment came to the same basic conclusion. One should point out, however, that the power surge of 1987 (which resulted in 49 homeruns for Andre Dawson of the Cubs and Mark McGwire of the A's tied for the highest total in the 1980s) may be attributed to differences in the ball. That year Rawlings manufactured the balls in Costa Rica instead of Haiti and it may be that it took some time for workers in the new plant to set the machines properly to produce consistent baseballs.

I think the principal reason that livelier balls are always pointed to as a culprit is because of the association between livelier balls and the homerun explosion of the early 1920s. In reality, although "a better quality of yarn was available after World War I the effect was not dramatic" (James, The New Historical Baseball Abstract) . The true reason that homeruns increased was threefold:

1. Babe Ruth had initiated a new style of play that fans responded to and that other players emulated, namely, taking a full swing at the ball and holding that bat at the end. One bit of evidence for this is the often told story of Ty Cobb adopting Ruth's style in a game and hitting three homeruns to show writers how easy it was

2. The owners, fearing a backlash from the Black Sox scandal just breaking at the end of 1920, did nothing to prevent the new style of offense from being adopted. Baseball being inherently conservative would likely have taken measures to squash Ruth in less turbulent times

3. When Ray Chapman was killed by a Carl Mays pitch in 1920 the league began to direct umpires to keep newer and therefore whiter and livelier balls in play. This also led to the ban in 1921 of the spit ball, shine ball, and other forms of defacing the ball that had been popular since just after the turn of the century. As a result pitchers had to learn how to more effectively make the ball move without the aid of foreign substances

Incidentally, Nathan has on his web site a talk "How Does a Baseball Bat Work?" where he offers the following simple equation for estimating the speed of a hit ball:

Speed of ball on impact = (.2 * vBall) + (1.2 * vBat)

The thing to notice is that the speed of the bat is much more important than the speed of ball. Hitters with increased strength can bring the bat to greater velocities through the strike zone thereby putting the ball in play at high speeds which result in more homeruns.