That question: “Are birthdays distributed evenly throughout the year, or are people more likely to be born in certain months?”

IO9 has part of the answer, via a heat map by NPR’s Matt Stiles that, in turn, was based on a table published in the NY Times showing the rank, in terms of births per day, of each date in the year (using US birth data, 1973-1999).

That’s interesting and all, but it leaves out a key bit of data: What’s the actual birth volume per day? I’d expect some minimal variation — no data set is perfectly even — but the ranking really only interesting if there’s meaningful variance.

Stiles noticed, and so his follow-up post shows as much birth volume data as he could get his hands on. The answer turns out to be that while September remains the most popular month in which to be born, it’s not by a meaningful margin. Generally speaking, the birthdays really ARE more or less evenly distributed.