A May Birthday: So That Explains Why I Was Such a Lousy Baseball Player

My college friend Greg Spira writes in Slate about the exaggerated share of American-born Major League Baseball players with fall birthdays.

This is more evidence in support of the idea that arbitrary eligibility cutoffs for youth sports programs have long-term impacts on who invests in the sport and eventually reaches the highest levels.

One of our earlier Freakonomics columns in the New York Times talked about this phenomenon in soccer.

I wish I could blame my baseball failures on my May birthday. In actuality, I think there were more proximate causes:

First, I was embarrassed that I needed glasses. So after my parents dropped me off, I would take off my glasses and put them in the pocket of my uniform instead of wearing them. I’m sure I would have been a better hitter if I could have seen the ball. (As an aside, it shows just how much times have changed that my parents didn’t stay for the games of their 7-year-old.)

Second, I idolized Jack Nicklaus, who used an interlocking grip when he played golf. I decided it would be a good idea to use an interlocking grip on the baseball bat, too.

In retrospect, that probably was not too smart.

john rickert

>How do those birthdays compare to the US Index?
the CDC publishes some of these birth statistics for recent years
(e.g. http://www.cdc.gov/nchs/data/nvsr/nvsr56/nvsr56_06.pdf for 2005)
to the nearest thousand the number of births in Jan-Dec of 2005(table 16) were
331 310 349 332
346 351 357 369
363 344 335 348
more in August, but third most in July.
The data for 1997 was a little different (the lowest rate observed in 60 years)
Table 15:
317 292 321 314
330 322 347 339
334 328 307 329
Certainly not near the variation in number of MLB players.


Here's an ESPN article mentioning the cross-handed thing: http://espn.go.com/sportscentury/features/00006764.html

I've heard the story several times from different places. Aaron hit cross-handed through high school/amateur baseball until he got to the minor leagues, when some hitting coach probably straightened him out.

Some say that hitting cross-handed may have improved Aaron's wrists and helped him become the home run champ, but I don't know that for sure and that sounds like faulty causality to me.


Pre-wikipedia and sportingnews.com (OK probably 30 years ago when I was in my late 0s), I learned from reading printed material derived from trees and ink that Hank Aaron used to work as an ice delivery boy. From carrying these bags of ice, his natural grip was to cross hands when he started playing baseball. Please don't ask me for a reference because my elementary school library card has probably expired.


Are young kids with fall birthdays older than the rest? Why does it matter if your birthday is in the fall or spring? Does that maturity really make that much a difference? I'm having trouble understanding this.


Hank Aaron used to hold the bat cross-handed (i.e. he was a right handed hitter but had his left hand higher than his right hand) and look how he ended up! I think you're clutching for straws...

Cyril Morng

Glad to see Greg getting some recognition here. He is a great sabermetrician and often shares insightful comments with the rest of us.


How do those birthdays compare to the US Index? If the point is that baseball players differ from the greater population, shouldn't we have some baseline here?

It's an interesting article, but it's pretty much useless with that basis.


My July 23rd birthday killed my chances. Now I play tennis (as a college student), but baseball is still my favorite sport.


This information is very interesting and reflects trends I see in my son's elementary school, many parents are now purposely holding their kids back from starting kindergarten at the scheduled time. Especially those kids born in the fall when there is a December cut off for school. As a result some children are over a full year older than others in the grade, not automatically have an advantage physically but most are indeed advanced in size and understanding. On the other side of the spectrum, our little league cut off is the end of April and my son and his friend are indeed close to that date and always the youngest on the team and the coaches don't see that. But I do also see that kids whose parents love a sport will be better at that sport, mainly because the parents will go out with them and play and the kids love the positive feedback from the parents, on most teams the coaches kids are among the best. So I think in the end its nature and nurture.



About 30 years ago, my wife, son and I were in line to visit one of the castles in Scotland. An elderly lady behind us remarked that our son, who was 5 at the time, must be a "summer baby," which he was: born July 30. "They start slow but catch up later, then they pass the pack," she said. She told us she was a retired elementary school teacher and had observed the phenomenon in thousands of youngsters. She was right in this case; my son graduated in the middle of his high school class, the top quarter of his college class, and was magna cum laude in his law school class. Has anyone looked into this matter?


Fortunately for my son, the age cutoff in competitive baseball around Texas is the first of May. He has a May birthday and he's actually the oldest kid on his team. He is also one of the biggest and better players on a highly ranked 7 year old team. Don't get me started on how odd it is that there are people who rank 7 year olds, but they do. His age does help him as you can see the difference between the older boys and the younger ones. It also helps that he doesn't interlock his grip either!

Ho Chi

You watched golf at 7 years?


I'd be curious to know how many children of former Major Leaguers themselves made it to the majors in time for this study. If there's a significant number, then the timing of baseball's offseason might also have an effect. Nine months from November would be August.


#3, did you not read the article in Slate? Kid A is born in August of year X. Kid B is born in July of year X+1. Ever year in little league, Kid A is 11 months older than Kid B. (This 11 months of development makes a huge difference if you're talking, say 9-year olds.) Kids A is more developed each year, thus is better each year, thus gets more attention & playing time. Therefore, Kid A has the advantage from like age 7 through age 16 (or more).


Am I missing something here, no where in the article does it say that the number of male births are consistent across the months. For all we know, there could be twice as many males born in August than in July and the therefore July born males actually have a greater likelihood of making it to the majors.


I remember a story about Hank Aaron crossing his hands, but by the time he was in the majors he held the bat the normal way. A quick google image search shows this.

I also have a May birthday, and I assume that is why I never made it in the big leagues.
Either that or the fact that I shredded my knee in my first little league at bat.
Either that or my general lack of athletic prowess.
Yeah, it's probably the third one.


@Alex #3: Yes, if the cutoff point for participation in a children's league is July 31 of any given year, then the August kids in the group will be essentially a year older than the July kids. At ages 9-13, that makes a heck of a big difference. The August kids are therefore more likely to be league stars and more likely to keep playing.

What's interesting is that in 2005, the little league cutoff date shifted to April 30, giving an advantage to the May/June/July birthdays -- the kids who were at a disadvantage for the last 50 years. Come back in 20 years and you should see the shift in MLB stats.


What I find oddly missing from this discussion is the Zodiac factor. We try to come up with eligibility cut-ff dates and the such like, but might it not be that certain signs are just more gifted (in general) in certain sports.

And it may have to do that kids born in a certain part of the year were not given the same exposure to baseball (e.g., someone born in say, March, isn't going to "bond" with football in those first, very important days of life).

I am surprised that you would overlook this very possible explanation and rely soley on science and reason. Just crazy!

There's also the sexual cycle.... Most kids are born in August (most adults, too). This means that the parents took a very conventional approach--i.e., it's cold, we can't play baseball, you look inviting in that flannel gown.... These kids (August/Leos) are born right in the middle of baseball, as are all winter-conceived children.

But those children conceived in summer and fall (and born in spring) are born to parents who, with all the weather on their side, and COULD have been watching or attending a baseball game, instead chose to, as I understand the phrase, "get jiggy with it," well, these children are obviously getting their DNA from people who COULD CARE LESS ABOUT BASEBALL! And if Freakonomics has taught us anything, it is the importance of genetics.

Eligibility cutoffs, my foot! These kids are doomed by their DNA to be the little kids that stand crying in right field, with a glove three sizes too big, and who wouldn't know what to do if the ball came to them...or if they actually got a hit.

Of course, in South America, the seasons are different--but the have baseball in the blood, so it doesn't matter.

Another solution from AaronS!



They say that kids born in the fall tend to be healthier and better at sports because that means that the mother was pregnant with them during the summer. A summer pregnancy means that the mother had easy access to all sorts of fresh fruits and vegetables that provide essential nutrients for the baby while it's in utero.

Jon Peltier

jholgate (#2) - Where did you get your information? Here's a picture of Hammerin Hank batting: