US Fertility Trends by Month and Year

I came across this beautiful data visualization heat map of live births by month and country/region, and I decided to recreate it for the US but by year. The figure below shows the frequency of births from 1972 to 2014, with darker boxes indicating higher incidences of fertility. The data is from the UN. (PS-Tableau and WordPress are annoying–if you don’t want to pay for extras. I can’t embed my table without the play sign in front it. AND it has a broken link *sigh*. So, please see twitter link ^_^).

I was somewhat surprised by how much the timing of fertility by month has stayed relatively consistent over the past 40 years. I expected more variability starting around the 1980s, as marriage rates declined and nonmarital fertility increased. However, the most common birth months in the US has consistently remained July through October, suggesting most babies are conceived through late fall and early winter. Looks like holidays are good for baby-making.