Warm colors = higher fertility rates, cool colors = lower fertility rates. 3 major wars (Franco-Prussian War, World War I, World War II) stand out, as do more recent events like COVID.

Posted by aar0nbecker

26 comments

  1. French fertility trends by month from 1861 to 2023. Warm colors = higher fertility rates, cool colors = lower fertility rates. More charts posted here as comments since Reddit is giving me a hard time with image uploads.

    Data is (births in month) / (number of days in the month) / (number of women age 15-44) * 100k

    The “general fertility rate” is usually expressed as the number of live births per 1000 women age 15-44 in a given year; I scaled the daily fertility rate per 100k women to get whole numbers. 15-44 is the age range used by the UN. I aggregated single-year age groups from the Human Mortality Database and linearly interpolated between censuses.

    Three major wars stand out: the Franco-Prussian War (1870-1871), World War I (1914-1918), and World War II (1939-1945). France had its own post-war baby boom after WWII, which has had echoes in the early 1980s and around 2010. Even at this scale you can see the effects of COVID in late 2020 and early 2021. I’m curious to hear what other patterns you see (I’m not an expert on French history).

    Inspired by a post by Aaron Penne from 8 years ago on monthly USA birth rates. Data availability has improved drastically since then, yet `matplotlib` has not.

    I used the `turbo` colormap in matplotlib because it was designed to make subtle value differences visible… does it work here?

    Source: [Human Mortality Database](https://www.mortality.org/)

    Tools: python, polars, matplotlib

    I’m working on a series of these heatmaps for other countries and am looking for feedback on the approach, formatting, labeling, etc. I’ll post the code and data in a GitHub repository soon, probably with another country’s heatmap tweaked as per your suggestions.

  4. This is really interesting. You can clearly see WWI and WWII. Any insight into what the blip on the radar in 1871 is? I’m not up on my European History.

  5. This heatmap shows the seasonality of births from 1861 to 2023. The seasonality heatmap shows the percentage of each year’s births in each month, but I scaled the monthly averages to a 30-day month and the annual average to a 360-day year so that February had a fighting chance. Births seem to have shifted from spring to summer/fall roughly since the introduction of birth control.

    https://preview.redd.it/69h29r5qbn0g1.png?width=9243&format=png&auto=webp&s=68866cf79f5086399a35251d054f8c2687eca565

  10. Interesting that birth rates didn’t decline nearly as much during WWII as WWI. Probably because it was the country was occupied rather than having all the men on the front?

  11. If anyone wonders, the Veil law in France was passed in 1974, making the contraceptive pill reimbursed by social security.

  12. “I wonder what happened in the 1910’s and 40’s?”

  13. I’m surprised that the WWI dip is bigger than the WWII dip. I guess because France was occupied as opposed to actively on the front lines. While there was fighting all over, everyone was home at night…

  15. That’s a fascinating chart, and beautifully presented. Thank you.

  17. Funny, they used to fuck in May-July (kids in Feb-May), then it shifted to July-Oct (kids in Apr-Jul), and today it’s slightly fuck in Nov-Feb (kids in July-Oct); or at least “fuck with the intention to procreate” for the latest period.

    A yearly normalized 3D line plot should better show the shift.

    edit: didn’t see the other graphs, they show the shift perfectly.

  19. Everyone just stopped hooking up in the fall of 1871 and then got right back to it again.

  20. Cool!

    What happened in France during the latter half of 1940 in wwii? Was that the nazi push into France?

    The Franco Prussian war, WWI and the advent of hormonal birth control are really apparent on the chart.

  21. Why were more babies born in Feb. and March in the past? More sex in May? And I wonder why that seasonality has kind of stopped or even reversed in the modern era?

  22. Looks like people did sex in the summer 200 years ago !!

    now people do sex in Autumn. Summer too hot !

  23. Interesting! You can see the Franco-Prussian War, ww1/ww2. And birth control maybe? 1975 looks like a delineating year?

  26. Interesting, France started slowly decreasing around 1900 and outside of the 30ish years between 1945-1975 just kept declining.

    I swear this isn’t that much different than the US and UK data but I got to find it. It almost makes me wonder what happened around the world around 1900 that changed everything.

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