Birth rates have varied over time, but especially prominent is the "baby boom" after WWII.
This boom is especially visible in new data collected by researchers at the University of Michigan. They digitized 78 years of monthly birth records from every U.S. state.
From the data they created this chart of the average birth rates in different states, in three different eras: Pre-baby boom era (1931-1945), the baby-boom era (1945-1954) and the modern era (1965- 2008).
You can see how drastically the birth rates changed. The redder the state, the higher the birth rate (2.14 babies per couple and above, up to 3.16). The darker the blue the lower the birth rate, from 2.14 down to 1.12 babies per couple.
The chart is from a new study in the journal Proceedings of the Royal Society B: Biological Sciences. The researchers say it's "the most extensive spatiotemporal data set on human births to date."
They actually used the data to analyze when birth rates peak in different places, and used the data with a model of measles infection to see the best time of the year to vaccinate.
This information can be used to time vaccination to reduce the burden of disease in developing nations.
SEE ALSO: Why Northerners Are Born Earlier In The Year Than Southerners
SEE ALSO: Peak Birth Month And Latitude Are Incredibly Closely Linked [CHART]