Which is the most common birthday?

A heat graph, which corresponds the number of births on any given day to light and dark squares, shows how American birthdays rate against each other.

Using Harvard University data, the graph shows September 16 as the most common birthday in the U.S., while December 25 and February 29 are the least common.

The heat graph, while telling you how popular your birthday is, also successfully tracks trends in the data.

Evidently, a large proportion of babies are born in September, with the top ten birthdays falling within the autumn month.

Possibly confirming suspicions we have long held about conception trends, September is nine months after the holiday season.

The least common birthdays fall at the beginning of January, at the end of November, and around Christmas time.

Interestingly however, December 30 is a more common birthday.

While July, August and September are very popular months for birthdays, it is somewhat notable that July 4, Independence Day, appears to be an obvious uncommon birthday in the U.S.

It is possible that with a reasonably high proportion of births being induced in the U.S. (a number which rose from 10% before 1990, to 22% from 1990-2006), obstetricians and expectant mothers may choose to schedule a birthday outside of this holiday.

The graph, which shows every day of the year, from January 1 to December 31, along with a ranking based on how many babies were born in the U.S. on that date, was made from data taken between 1973 and 1999.