Where are the kids born in December?

This is the question Xavier Sala i Martín made in a catalan TV show about economic sciences (yes, pretty cool you can talk about that in the TV!). In a nutshell, he described the relative age effect. A pattern for which most elite football and hockey players are born in the first 6 months of the year because young kids from a given age are put to compete together and the older ones are bigger and stronger. Then coaches dedicate more time to them, and by the time the physical capabilities are even among all kids born the same year, kids born in January have trained more, get more positive reinforcement, etc…

But he did not answer where are the kids born in december. I speculated that those “bad” at sports would have more time to do arts, like play music. Lets test the hypothesis! I found a list of Musicians by birthday in wikipedia and @vgaltes scrap it for me*. Amazing! 57% of musicians in wikipedia are born in the latests 6 months of the year (yes, a chi square is highly significant with this sample size), and january is the only month that goes against our prediction.

Rplot03

Each bar is the number of musics per month starting in January. Black line is the expected number. Sorry for the terrible graph with no axes.

We should have stopped here. Publish it and be famous. Unfortunatelly we got excited. @vgaltes found this web page with lots of birthday summaries by profession and by eyeballing the numbers there is no clear pattern for musicians. Then @dukjb started pointing out that we should correct for number of days that each months has, and more importantly, for the natural birth rate per month, which is likely not uniform. Then we lost momentum, we got distracted by other things and the conversation fade out. But at least we had some fun, no excuse for being bad at sports** and this post!


*I am ashamed, but It would be too time consuming to do in R for me for a side, side, side, side project.

**I was born in early April.

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One thought on “Where are the kids born in December?

  1. Tots ens varem quedar amb la conclusió i en la pregunta on eren els nens del Desembre i tu has anat mes lluny. Suposo que el investigador surt sempre. Felicitats

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