The Most Popular Birthdays

Not all birthdays are equally likely.  I've delved through 20 years of births data to analyse it and below I present a graph of the average number of births for each date. The average to compare all of these births to is 1800 per day:

The 29th of February is excluded from the chart, but came in at just under a quarter of the average.

There are some noticeable peaks and troughs. Firstly, September is the most likely month for people to be born in, with the 26th of September being the most common. Eight out of the ten most common birthdays fall in this month. There are two reasons for this. Firstly the average gestation period of a human is about 280 days which puts the time of conception firmly near Christmas day and the days off that go with it. Secondly, with the advantage that comes with being one of the elder in a school year, many parents aim for dates in September.

The lowest dates are mostly in the Christmas Holidays, with a few around New Year's. Boxing Day is the lowest at around 1360 births on average (compared with around 1800), with Christmas Day climbing to 1420 and New Year's Day coming in third at 1570. This is because elective procedures such as some caesareans and induced births are left until the holidays are over.

Another weird quirk is that the 1st of April is significantly below the other dates around it. This could be because parents are trying to avoid April Fool's Day.

Of course, the best birthday to have is the 18th of May...