France may have been the first country in the world to undergo the "demographic transition", a period of rapidly declining birth rates. Contrary to popular belief, the birth control pill is not necessary for this to happen and many countries, including the United States, underwent the demographic transition before the invention of the pill.
Find it interesting that for most of World War 2 birth rates were actually increasing and that they never got as low as the levels experienced during World War 1 (specifically 1917).
Also curious about the sudden sharp drop in birth rate in the late 1940s in the UK. Seems like the opposite of a baby boom.
The WWI lows are really something. You can see just how bad things got in France. I have to imagine the men who survived intact got their choice of brides in the 1920s due to a very tilted gender ratio.
The demographic effect of WWI on France has been widely studied; among the conclusions -- a million children were "missing" that is, without the effect of the war and soldier death a million children would've been born, 25% of all men born in 1894 died during the war years and number of widows doubled over the usual rate. Some theorize the lack of males led girls to lower their standards and less qualified men (genetically) had more children than usual and this lowered the quality of soldiers twenty years later in WWII - but that's a stretch.
Also curious about the sudden sharp drop in birth rate in the late 1940s in the UK. Seems like the opposite of a baby boom.
Outside of sub-Saharan Africa and a few other countries, fertility rates are low and getting lower.