I was reading about birthday problem and I found a statement that real-life birthday distributions are not uniform since not all dates are equally likely (last line of first paragraph of section 'calculating the probability').
Here I do not understand why all dates are not equally likely. Long time ago I read that every second 3 babies are born. On this basis I don't think that all dates are not equally likely.
Kindly help me understand what mistake I'm making? Thanks.
On
The cited statistic, "every second 3 babies are born" is just a rough average. In truth, human birth rates are extremely seasonal (the weather having a dramatic effect on human behavior). Here is a reference:
http://www.sas.upenn.edu/~valeggia/pdf%20papers/birth_seasonality.pdf
When someone says that a baby is born every (instert a period of time), they actually mean that this is true on average. It can happen in a small village that three babies are born on the same day.
Many of these deviations from the average get washed out if you have enough data. But some things don't. Several things affect when people are born. A mother's physical and mental condition depend on periodically changing things like the weekly and yearly rhythm of her life. People are not equally likely to mate at all times. And you can probably find or think of many others.