A friend posted an interesting data table on my Facebook wall yesterday, which was my birthday. The data listed each day of the year with a ranking for how many babies were born in the United States on each date from 1973 to 1999. Some interesting trends are evident in the data. Apparently, people like to make babies around the winter holiday season because a large proportion of babies are born in September (ours is due Sept. 24, btw).
Sept. 16 was most common. Feb. 29* was least common. This heatmap is an effort to visualize the trends, with darker shades representing more births:
Data source: NYTimes.com, Amitabh Chandra, Harvard University
* A previous version of this post incorrectly listed Jan. 1 as the least common birth day.