Birthday Trends

Triggered by a conversation yesterday, I recently pondered on the statistical trends of birthdays. I noticed that a large number of my co-workers have birthdays in May, July and August. Following are some numbers to consider:

Both sets of statistics are the relative percentage of birthdays per month for a given population. See <http://pressroom.hallmark.com/birthday_trends_stats.html> for more on birthday statistics from Hallmark. I obtained the Galdos Systems birthdays by looking at the company calendar and doing some quick calculations of the 25 people listed there. I labeled Galdos as "Global" since many employees are not Canadian born, while Hallmark seems to be predominately American. As a result, these numbers vary a bit (plus the fact the sample size is so small for Galdos Systems).

I also compare this with Taiwan, where most of the birthdays (as I observed) are in November and December. This is a convenient 9 months after Chinese New Years (quite often the only holiday some people take in Taiwan). Where as the Hallmark and Galdos data show 9 months previous to be around Christmas and August (after the kids start school?) respectively. The difference is small but is seems to be a slightly greater probability of people having children 9 months after a major holiday over other times in the year.

Important Question: Should we be a little more careful to knock before entering a room during the holidays?