How Frequent is Your Birthday?

In: Culture Science

28 Nov 2012

Very nice heat chart. I wonder what would happen if you filtered by geography? An awful lot of people I knew in northern NY were born 9 months after the cold dark winter.

More colorful Tableau version:


8 Responses to How Frequent is Your Birthday?



November 28th, 2012 at 1:09 pm

Would be interesting if the scheduled births were removed – the July 4/5 gap is interesting … fewer scheduled c-sections? Same with the time around Thanksgiving and Christmas.



November 28th, 2012 at 2:23 pm

So a lot of people conceive during October/ December. I assume the thing about the holidays is women managing to hold off for a few days (or alternately inducing it in the previous days but there’s much heavier coloration right between Christmas and New Years), kind of like the drop in the death rate such before New Years (especially in 1999) and the subsequent surge.


Rick Wicklin

November 28th, 2012 at 3:18 pm

To see a smoothed version of this chart, see

Also, the previous comments refer to holidays. The effect of holidays on US births is quite interesting! See



November 28th, 2012 at 7:21 pm

It would also be very interesting to see this for a Southern Hemisphere country like Australia. The moderate climate might make the seasonality less pronounced.



November 29th, 2012 at 1:17 am

I’d like to see a version that’s counted back so we can see the most popular conception dates!


Beth (@DataGeekB)

November 29th, 2012 at 8:39 am

There is a distinct seasonality to birth data, and yes it is opposite in the northern and southern hemispheres.

September is the most frequent birth-month in the U.S. The pattern is more pronounced when you adjust for the varying number of days per month.

I have a blog post on this topic, with links to source data, if you’re interested in more details. (Will provide link upon request rather than risk seeming like a spammer! Or just visit my blog and look for the 9/7/2012 post.)



December 1st, 2012 at 9:42 am

This would be even stronger if the color range had some legend. How much variation are we seeing? Does the range from dark to light represent 5%, 50%, or 500% variation? To go back to the legend that is provided, how much more common or less common are we talking about?



January 7th, 2013 at 4:41 pm

Forget about july 4/5, how about the 13th!? Are people (well, women ;)) really that superstitious that they’ll squize one in longer/out sooner just to avoid having a baby being born on that day?

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