Slender Bats, or How a Rule Change May Have Contributed to the Year of the Pitcher

For those of you who spent this past season slumbering in a cave, countless analysts and talking heads hailed 2010 as 'The Year of the Pitcher.' This stems primarily from the fact that there were six no-hitters last season, two of which were perfect games, as well as a near-perfect game (in which an umpire unfortunately blew a call on what would have been the final out of the game) - that is not to say, however, that that label is without merit. Runs scored dropped by about five percent, home runs by around eight percent, and earned run averages dropped by nearly six percent. While offensive numbers do ebb and flow from year to year, it is intriguing to combine these factors, particularly on the heels of the so-called 'Steroid Era' as testing has become more rigorous and pervasive. Could there be another reason or factor for this fluctuation? Nick Scott of Royals Authority may have discovered a contributing factor here.

I was recently looking at the Official Rules of Major League Baseball and on page number four they have a section titled “Changes for the 2010 Major League Season”. I hadn’t recalled reading anywhere about notable changes to the rule book in 2010, so I reviewed the items to see if any major changes had been made. The first few changes were about how to draw the lines of the field and the coach’s box, again nothing of real importance. However, the fourth bullet point read:

“Reduced maximum bat diameter to 2.61 inches. (Rule 1.10(a))”

So I then went to rule 1.10(a) and read the following:

“The bat shall be a smooth, round stick not more than 2.61 inches in diameter at the thickest part and not more than 42 inches in length. The bat shall be one piece of solid wood. Note: No laminated or experimental bats shall be used in a professional game (either championship season or exhibition games) until the manufacturer has secured approval from the Rules Committee of his design and methods of manufacture.”

In the 2009 rules, the bat was allowed to be a maximum of 2.75” in diameter. The last time the maximum diameter of the bat had changed was 1895 when the size changed from 2.5” to 2.75”. Therefore, the allowable bat diameter shrunk by 5.1% in the off-season immediately prior to the “year of the pitcher” and it was the first time such a change had been made in 114 years.

Considering the amount of time and money put into baseball analysis, I am shocked that it took this long for someone to point out this rule change, however minor it may appear. While Scott's findings are far from conclusive I cannot believe that this did not have some impact, however minor, on offensive output in 2010. I recommend that you check out the article in its entirety, as Scott links to a wealth of other sources, some of which expand on his findings, to boot.