Birth Month Effect On Baseball Players, Part I

The birth month phenomena is an interesting occurrence that is applicable throughout society.  While Outliers by Malcolm Gladwell implied the same was true for baseball, I wanted to take a closer look.  Looking at the birth month of every MLB player that has appeared in a game since 1965, the graph suggests that you’re most likely to become a MLB player if you are born in August.

Among US born players, 12.2% of MLB players have birthdays in August, while only 6.4% have birthdays in July. A discrepancy that big can’t just happen by accident can it?  Not likely.  The reasoning is that the Little League Baseball cutoff date for 55 years (up until 2006) was July 31.

So what does that mean?  A player, for example, born on August 1, 1996 would be playing in the same division as a kid born on July 31, 1997.  Given the cutoff date, the kid with a birthday on August 1 is a year older than the kid with a birthday on July 31 yet they are playing in the same division.  Thus, the player with the birthday in August likely has an advantage in size, strength and maturity.  Players with birthdays in August may be more likely to get picked for All Stars, get advanced training and practice, and selected for more competitive leagues which ultimately helps make them a more successful player.

Interestingly, in 2006 Little League changed the cutoff date to April 31, so if you want your kid to have a leg up on the competition, a May birthday will be most beneficial.

So if players born in August are more likely to become MLB players, do they perform better at the Major League level?  Stay tuned for Part II in a few days.

Data Source: Sean Lahmans’ baseball1.com