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
It is often said that demographics is destiny.
Franklin accurately foresaw how America would outrun Europe. Young men could easily buy land, get a homestead and marry earlier.
Americans were thus having twice as many children as Europeans, who married less often and later. 4/9
Franklin wrote that through the force of higher birthrates, America would soon have more Englishmen than England.
By the power of compounding, with a doubling every generation, America would eclipse England as the great power, on land and at sea. 5/9
An abundance of territory meant that young Americans would not be stuck in cheap labor jobs but could get a place of their own early on.
Because the continent was so big, this dynamic could play out for generation after generation, and it did! 6/9
Amazingly, Franklin foretold the existence of high fertility sects like the Amish, who through a religious devotion to hard work, frugality and early marriage, would see "great increase"! 7/9
Franklin also wrote of his dislike of slavery on multiple fronts.
He said overwork and poor treatment "broke the constitutions" of slaves. But also, he explained how slaveholding was bad for the character of the people that held them.
He later became a leading abolitionist. 8/9
Seeing America's current birthrate woes, Founding Father, amateur demographer and pronatalist Ben Franklin would no doubt have some sage advice to offer on the occasion of America's 250th birthday:
(1) Marriage, and especially early marriage, are crucial for healthy fertility.
In turn, there need to be pathways to stable employment early on. If it takes too long to get established, people will marry late and have few children.
(2) Spread out on new land and embrace homeownership.
Franklin saw early on that when young people could get some land of their own, they would have large families and that crowding into cities was bad for birthrates.
(3) Embrace beliefs that teach marrying earlier and being "industrious and frugal"
Ben Franklin saw that certain beliefs lent themselves to higher fertility. Franklin would no doubt want to teach young people those values and would probably favor religious groups that hold those things. 9/9
Happy 250th! 🌎 🇺🇸
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A Swedish study published today looks childbearing by cohort, asking whether younger people are likely to have fewer children.
Starting with women born in 1990, each age group falls further behind previous generations in childbearing, suggesting much lower final fertility. 🧵.
This chart plots childbearing by age for each generation of Swedish women. The area under each curve will correspond to the completed fertility for that generation of women.
The group born in 1990 had peak fertility at age 30 and then began a steep decline, just like every generation before it. There is no evidence so far of a recovery in the 30s.
Assuming the 1995, 1999 and 2002 cohorts behave the same way, the area under those curves will be a lot less. That means that younger generations could have far fewer children. 2/5
Why is this happening? The author, renowned demographer @MartinKolk, can point to no domestic trends in Sweden.
Rather, young Swedes are being carried on the same cultural currents of social media that are experienced by young people globally. 3/5
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. 🧵.
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