h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

As a lad growing up Canada through the 1960's, I found it amazing how many classmates had birthdays within a 10-day span of my own. Later, it didn't seem odd at all.

January is about the coldest month of the year in many parts of this country. In the day, if people had TV, there might be as many as two stations to choose from. Drive-in theatres were closed at that time of the year, and far to far away anyway. Sit-down, indoor theatres were even more rare. There was no internet, no video games of any sort, ... And face it, on long and cold nights, there are only so many games of cards one can play, or even board games.

And so inevitably, a lot of kids found themselves born in October.

In brief (too late now, huh?) while the numbers in the article are perhaps mathematically correct, they are next to meaningless when general environmental variables are taken into account.