Happy birthday to you! It is your birthday, right? If you live in America, it more than likely is! As it turns out, Sept. 16 is the most common birthday in America.
The New York Times published a long table graph in 2006 that ranked every day of the year with how many babies are born on that day. The graph included all the babies born from 1973 to 1999, a huge sample size that was collected by a Harvard economist named Amitabh Chandra.
This collection showed that Sept. 16 was the most common, with Feb. 29 being the least common, since it’s a leap day, and with second most uncommon being New Year’s Day. If you don’t really want to scroll through that graph, you can check out this handy visualization of the data, brought to you by The Daily Viz’s Matt Stiles.
The most common birth month is August, unless you don’t count its extra day, then the most common month is September.
Though we don’t really know why so many babies are conceived in winter and born in autumn, a study published in Obstetrics & Gynecology came up with a few hypotheses, including deterioration of sperm quality during summer, seasonal differences in anterior pituitary-ovarian function caused by changes in the daylight length, and variation in quality of the ovum or endometrial receptivity. Or, it could be the increased sexual activity that comes with end-of-the-year festivities.
Whatever the case may be, happy birthday to you; you share this day with a lot of other people.