In the 19th century, something remarkable happened across Europe: people started having fewer children. It was one of the biggest demographic shifts in human history, helping societies escape the old cycle in which rising prosperity was quickly swallowed by population growth.
But France got there first.
Its fertility rate began falling around 1760 — roughly a century before the same transition took hold elsewhere in Europe. That has puzzled historians and economists for decades. France was still relatively poor, rural and largely illiterate, and the Industrial Revolution had barely begun.
So why did French families start having fewer children?
According to research by economist Guillaume Blanc, one important reason might be that people started caring less about religion.
The historical fertility transition first took hold in France *in the 18th century*, before the French Revolution and more than a century earlier than in any other country 🤔
— Guillaume Blanc (@gguillaumeblanc) November 29, 2021
Why religion?
When we think about the major changes experienced by human society over the centuries, we tend to focus around inventions or technological paradigm shifts. We talk about the “Iron” age, or about the Industrial Revolution. But demographic changes are just as impactful.
Before birth rates dropped in the past two centuries, improvements in the standard of living were offset by demographic expansion, with gains in production often translating into larger populations rather than permanently higher living standards.
It’s extremely curious that the demographic transition, an essential condition for development, took hold in France more than 100 years earlier than in any other country. The first consideration would be the Industrial Revolution, the transformative period that marked a significant shift from agrarian, handcrafted economies to ones dominated by industry and machine manufacturing. But the Industrial Revolution started in the United Kingdom, not in France.
×
Thank you! One more thing…
Please check your inbox and confirm your subscription.
When its demographic transition started, France was relatively poor (compared to its peers). It was also rural and largely illiterate. In fact, the UK saw a temporary increase in fertility right after the industrial revolution (around 1760), so this couldn’t have caused the decline in France.
So then what was it?
Blanc believes it has a lot to do with religion. In his research, he used crowdsourced genealogies to comprehensively document the decline in fertility and places its onset at around 1760. He then compared that demographic shift with several measures of religious change, including religious language in wills, donations to the Church, recruitment into the clergy, and the names parents gave their children.
“In aggregate-level evidence, relying on the work of historians I document an important process of secularization that took hold at the same time in France,” the researcher explained on Twitter.
“With dechristianization (in the mid-18th century) the Catholic Church lost influence and could not oppose fertility control—coitus interruptus—anymore,” the researcher adds.
The idea isn’t that 18th-century French couples suddenly discovered contraception. Rather, Blanc argues that the weakening authority of the Catholic Church relaxed some of the moral and social constraints surrounding deliberate fertility control.
Image credits: Coale and Watkins (1986).
The loss of influence of the Catholic Church is first attributed to a backlash against elites. In particular, people started becoming more antagonistic towards religious authorities associated with an absolutist, “divine right” monarchy. Even before the French Revolution happened, this antagonism grew.
Secularization had a larger impact in more densely populated places, and wherever it had a larger impact, fertility rates dropped faster.
But that’s not the only surprising factor.
Then inheritance laws changed the economics of having children
In 2026, economists Victor Gay, Paula Gobbi and Marc Goñi published evidence that the French Revolution itself substantially accelerated the fertility decline — not through revolutionary ideas alone, but through inheritance law.
Before the Revolution, inheritance rules varied dramatically across France. In some regions, parents could leave most of their property to a single heir. Elsewhere, inheritance was already divided more equally among children.
Then, in 1793, revolutionary reforms imposed equal inheritance among all children, including daughters. For families owning farms or other assets that were difficult to divide, having many children suddenly carried a new cost: the family property would be chopped into increasingly smaller pieces.
The researchers could use those pre-existing regional differences as a natural experiment. They compared areas where the new law radically changed inheritance practices with areas where inheritance was already egalitarian. Using both historical family reconstructions and crowdsourced genealogical records, they found that the reforms reduced completed fertility by roughly half a child in affected regions.
Women in those areas also married around 1.9 years later, and families appear to have used several strategies to limit fertility.
The effect was large. The authors estimate that inheritance reform accounted for up to 46% of the fertility decline during the first phase of France’s demographic transition and about 36% across the transition as a whole.
This doesn’t disprove Blanc’s argument. It just goes to show that both economic and social factors played a role, in ways that often aren’t easy to understand.
Why France’s head start mattered
This carries some remarkable implications. For starters, if France had followed the same demographic trends as the UK (the two countries are similar in many economic ways and are often compared), it would have 250 million inhabitants now. Currently, it has under 70 million. Secondly, although the UK was the cradle of the Industrial Revolution, and although the country made impressive inventions that elevated the country’s economy, the economies of France and the UK grew at a comparable rate during the Industrial Revolution.
This demographic change in France was a pivotal moment not just for the country, but for the entire continent, given how influential France has been in Europe. In fact, given that what followed was a colonial age where both the UK and France played active roles, this event probably affected the entire world.
It’s not just technology that enabled an increase in living standards. Lower birth rates were a major reason for increasing standards of living for most of mankind’s history.
This article was originally published in October 12, 2023, and has been edited to include newer research and update the framing to reflect a more complex interaction between cultural change and economic incentives.
