How Common Is Your Birthday?

It was 2 a.m. and my kid has just fallen asleep. I was frazzled after a long day of dealing with a fiesty toddler and all I wanted to do was sit on the couch and drown my frustrations of having a strong-willed child with a pint of ice cream and some mindless TV. I was aimlessly flipping through the channels when a promo for a show stopped me in my tracks. The text in the video read, “18 million people in the world share the same birthday” and the wheels in my head churning. I wondered how many people I share a birthday with.

The answer? Way more than I thought considering that my birthday falls on a holiday.

A statistician put together a chart of all 365 days of the year based on the total births on each of those days between 1973 and 1999 and discovered some really fun stuff like that the least-popular date for birthdays was February 29th, obviously since it only occurs once every four years on a leap year, when there are actually 366 days in a year. The second least popular day is December 25th.

The most popular date for births is September 16th.  That's just about nine months after the holiday season.  And actually, all ten of the most common birth dates are in September. September 11th is the 24th most common, but that's now dropping. July and August have the second and third most births.

Generally, major holidays have a lot fewer births around them- people really don't induce labor on those days. July 4th has the fewest births of any summer day, and July 5th is second. Thanksgiving and New Year's Day are don't have a whole lot of birthday, although the date of Thanksgiving changes every year. The only exception of holiday births is my birthday, Valentine's Day.  Believe it or not, Valentine's Day has the most births of any day in the first five months of the year.

[via NBC/The Daily Viz/VizWiz]