What caused the Baby Boom? To fix today's low birth rates, it helps to know how falling fertility was turned around once before.
Economic growth helped. But it turns out there a cultural closeness between men and women unlike anything before or since! A🧵, please share, follow!
A widely read article explained how new appliances, medical progress and more housing all supported family formation.
But this can't be the whole story, because usually as people are better off, fertility goes down.
There was something special in the air at the time. (2/9)
World War II saw young men involved in the war effort at incredibly high rates. In the US, 25% of men and close to 50% of men ages 18-30 served in the military and a further 25% were employed in war work. Other countries had similar or higher rates of deployment. (3/9)
Young men were seen by young women in a glowing light, both during the war and after returning home. Young men also matured quickly. What followed was an era of warm feelings between men and women across society, that infected a generation. (4/9)
In those days, love meant marriage. And so people married more often and earlier than ever before. In the US, women married at a median age ~20 and 94% of men and women married by age 40!
It turns out that lots of marriages at early ages are the key to high fertility. (5/9)
Economic tailwinds helped. But it takes culture to truly explain how births soared in so many different countries around the same time. (Chart from @WorksInProgMag.) (6/9)
If more and younger marriages gave us the Baby Boom, are they an answer for today? Yes, and here is important thread on that! (7/9)
You can get a sense of the very positive atmosphere that existed then between men and women by watching clips of couples from that era.
Here is a couple who married in 1941 and served in the war, talking about love after their 77th anniversary. (8/9)
If you enjoyed or learned something from this thread on the causes of the Baby Boom, and lessons for today, please repost. Also follow and spread the word about this account, which is dedicated to solutions to our fertility crisis. (9/9)
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TESTOSTERONE SUPPLEMENTATION DRASTICALLY LOWERS SPERM COUNTS
Men who want more children should not do it.
Numerous studies find that exogenous testosterone sharply reduces testosterone production within the testes, effectively shutting down sperm production. 🧵.
A World Health Organization study found that among 271 healthy and fertile men, a large majority became azoospermic (a condition where a man's semen has no measurable sperm) with testosterone injection.
There was just one pregnancy in 1486 cumulative months of study. 2/6
A literature review published 2013 explained the mechanism:
"Exogenous administration of testosterone results in negative feedback leading to inhibition of FSH and LH production. As a result, intratesticular testosterone levels (ITT) decrease." 3/6
The leftwing, blank-slatist economist Daron Acemoglu sees how rich countries have low birthrates and argues that low birthrates cause growth and innovation. 🙃.
The opposite is true. The evidence shows larger populations have more innovation and higher economic growth. 🧵.
In his remarkable 1755 publication Observations Concerning the Increase of Mankind, Ben Franklin put on his demographer hat and foretold the rise of America to superpower status some 21 years before the signing of the Declaration of Independence. 🇺🇸 🇺🇸
🧵, please share!
Franklin worked out demography from first principles.
He began with the observation that marriage drives population growth, and marriage in turn is driven by the ability of young men to support a family. He saw that when people marry early, they are able to have more kids. 2/9
All the way back in 1755, Franklin knew of the problem of low urban birthrates.
He lamented how people in cities delayed marriage and embraced single living and how cities were a population sink, with more deaths than births. 3/9
HOW VANCOUVER ENDED UP WITH THE LOWEST FERTILITY IN THE WESTERN WORLD
Vancouver, Canada had a TFR of just around 0.7 in 2025. That's the lowest fertility of any major city in the West, and one of the lowest anywhere on Earth.
What forces lead to such low birthrates? 🧵.
The story starts with culture. Canada quite a bit less religious than the United States these days, and that is a big reason why Canada's TFR at 1.25 is much lower than the US (~1.6).
But within Canada, BC in general and Vancouver in particular are especially irreligious. 2/7
The story continues with housing. Although Canada is big, the share of land that Canadians are allowed to build on is tiny, and that is especially true in British Columbia.
Some 95% of British Columbia is government-owned, leaving just 5% in private hands. 3/7