France was once Europe’s superpower, thanks above all to its enormous population. Its decline coincided with a collapse in its birth rate – now we know why.
In the eighteenth century, France was the China of Europe. But after a thousand years of dominance based on particularly fertile land, she declined over the next 250 years to be just another European power. Around this time, more than 100 years before the rest of Europe, French women began to have fewer children. In 1700, almost 1 in 25 inhabitants on Earth, and one in five in Europe, was French. Today, less than a percent of humanity is French. Why did France’s population decline in relative terms so dramatically, and did it really mark the decline of France?
The demographic transition is usually thought to be driven by economic forces, but – in France at least – culture came first. Using data from online family trees, my work shows how the loosening of traditional religious moral constraints in Ancien Régime France drove the decline in fertility, setting France off on a wholly different course from England, which was about to see a dramatic increase in its population.
From the dawn of humanity to the eighteenth century, human life was dominated by starvation, poverty, wars, and pandemics. It was nasty, brutish, and short, just like that of apes or any other animals.
Whenever innovations raised the productivity of land, labor, or capital – and these innovations did take place – these simply led to fewer children dying or more children being born, with the extra economic output used to feed more hungry mouths. This was the history behind Thomas Malthus’s bleak 1798 prediction, in An Essay on the Principle of Population, that, since population growth is geometric but agricultural productivity growth can only be arithmetic, humanity was doomed to constant subsistence, with growth in the population always outstripping its ability to feed itself.
Malthus’s prediction proved false due to two paradigm shifts working together: the industrial revolution and the demographic transition. With the industrial revolution, unprecedented technological advancements took hold. The pace of human technological, scientific, and economic progress increased significantly and the human condition changed forever. But technological progress was not working alone.
The decline in fertility during the demographic transition was also a turning point in human history, because it marked the escape from the Malthusian mechanism. Instead of simply allowing for more and more people, the technological innovations brought by the industrial revolution could lead to better living standards, and economic growth was no longer short-lived. Investments in human capital and mass education could take place following the decline, which further propelled societies on the path to sustained economic growth.
If we were to condense all of human history into one short telling, it would look like this: millennia of stagnation, then the industrial revolution (in the eighteenth century), then the demographic transition (in the nineteenth century), then sustained economic growth – the dramatic leap forward experienced by humanity in the past few centuries.
Broadly, this narrative is accurate. But for Europe’s first superpower it is out of order. The historical decline in fertility took hold in France first, in the mid-eighteenth century and more than a century earlier than in any other country in the world. At the time, there were 25 million inhabitants in France and 5.5 million in England. Today, there are 68 million inhabitants in France and 56 million in England. Had France’s population increased at the same rate as England’s since 1760, there would be more than 250 million French citizens alive today.
According to Alfred Sauvy, the French demographer who coined the term ‘third world’, in 1962, the decline in fertility is ‘the most important fact of the history of France’. France was eclipsed as Europe’s only real superpower by the relative growth of its rivals, most importantly England and Germany, in the nineteenth century.
France’s emergence as a major global power spanned several centuries, from the foundation and expansion of the Kingdom of the Franks under Clovis and Charlemagne in the fifth and ninth centuries to Napoleon. During the Hundred Years’ War in the fourteenth century, London was by far the most populous city in medieval England, but Rouen, only France’s second city, may have been as large as it.
By the seventeenth and eighteenth centuries, under the long-lived Louis XIV France boasted the continent's largest population and the world’s second largest colonial empire, after Spain. It was so dominant that it prompted multiple coalitions, or grand alliances, of all the other major European powers together to challenge it. And even then the first Grand Alliance was unable to make significant gains in the Nine Years’ War at the end of the seventeenth century. In the War of the Spanish Succession soon after, the French could field 400,000 troops at times, almost as many as the combined forces of the Holy Roman Empire, Prussia, England, and the Netherlands.
The gap in demographic power and military might stood perhaps at its widest during the French Revolutionary and Napoleonic Wars from 1792–1815. The French fought against most of Europe at once and could regularly field over a million soldiers, often outnumbering its opponents, which formed more than six successive coalitions before they could eventually prevail.
Rulers had worried about a projected depopulation of France since the seventeenth century, with the pronatalist Edict on Marriage of 1666, but it was not until much later that these demographic struggles became apparent. The prevailing view is that on 15th June 1815, during the Battle of Waterloo, France lost its position as the preeminent power in Europe. The influence of demographic factors was revealed most dramatically during the Franco-Prussian War of 1870, when France was defeated after a solitary battle against a single opponent. During World War I, the population and military gap had completely closed, if not reversed, and Germany had substantially larger forces than France.
And yet the early decline in fertility in France is not well understood. Economists tend to view economic development as the primary driver of the demographic transition, by increasing would-be parents’ incentives to invest in human capital instead of having children (trading quantity for quality). But France was still a developing country in the eighteenth century; it was mostly poor, rural, and illiterate, and one to two centuries behind England on all of these metrics, while about 30 percent of babies died before they were one, and half before they reached age five.
If it was not development that drove the French fertility decline, what else could it have been? Some research documents the role of cultural factors on historical fertility transitions, but France appeared to be a stagnant society before the French Revolution. If culture was not changing, then how could it be responsible for such a climactic shift in such an important social outcome?
Additionally, there is only extremely limited data available around the exact time that we know the fertility decline must have set in. Data on the number of children per woman, or on the sexual practices of peasants and ordinary people alike, is unsurprisingly hard to gather for the 1600s and 1700s. The data from modern censuses, only available after the 1830s, shows profound differences between France and the rest of Europe, but this data appears only after the transition had already happened in France, and the timing of the onset of the decline remained unknown.
In my research, I use big data from crowdsourced family trees on geni.com to comprehensively document the decline in fertility in France and its timing for the first time. Users of geni.com search for scanned handwritten birth, marriage, and death records of their ancestors to construct their family trees and upload them online. In 2018, a team of computer scientists and geneticists downloaded all publicly available profiles from millions of family trees.
A major caveat of these online family trees is that they mostly include vertical, intergenerational links because users are usually only interested in their direct ancestors. As a result, they often lack horizontal lineages (cousins, uncles, aunts, etc.), which are essential to measure fertility accurately since doing so requires a count of the number of siblings at each node of the tree. To deal with this, I identify and select trees with recorded horizontal lineages – that is, where some parents have a fertility greater than one.
I also carefully compare the genealogies to the best available representative data on urbanization, fertility, and mortality in 30 different countries – mostly from censuses, but also from a large number of estimates – and show that individuals in the genealogical data are, perhaps surprisingly, a representative sample of the overall population in the eighteenth and nineteenth centuries. Online genealogies therefore include ordinary individuals who lived at the time, such as Jean and Michel Rousseau in the figure above.
When census data becomes available, there is a particularly high correlation with geni.com, especially in countries with good archival records. In France, for example, all parish records of birth, marriage, and death are scanned and publicly available online from the seventeenth century onward – constituting the underlying, raw handwritten data on which users of genealogical websites rely to construct their family tree. The correlation between urbanization, fertility, and mortality in the geni.com genealogies and in census data is more than 95 percent.
Because modern censuses are only available after the 1830s, I also compare the genealogies to the aggregate statistics extracted from a large number of parishes in England, as it is the only country with excellent readily available representative data on the eighteenth century, and reach the same conclusions – further suggesting that online genealogies in France, relying on similar parish records, are accurate as well.
Using this genealogical data, I estimate that the decline in fertility took hold in France in the 1760s, more than a century earlier than in any other country. The average number of children per woman declined from more than 4.5 to 3.5 in less than 40 years. In the meantime, the average English woman was bearing six children. There, as in the rest of the world, the Malthusian mechanism was very much alive and would be for an additional century. In England, the industrial revolution made people richer, but they spent their additional wealth having more children.
So, the demographic transition took place exceptionally early in France, but why? In my research, I argue that the diminished sway of the Catholic Church, nearly 30 years before the French Revolution, was the key driver of the fertility decline. Since at least Tocqueville, and more recently Emmanuel Todd, we know that a sustained loosening of traditional religious moral constraints took place in the mid-eighteenth century, at a scale and extent that no other country has achieved.
How can we measure secularization at the time? In a pathbreaking book, historian Michel Vovelle studied the language used in invocations in the opening statements of wills to document ‘dechristianization’ in Provence, in the south of France. Whether it was dechristianization, secularization, or simply a loss of influence of the clergy is hard to say, but the data shows that attitudes toward life and death changed radically in the course of the eighteenth century.
At the end of the seventeenth century, most testators referred to God, Paradise, or various saints in their wills. On the eve of the French Revolution, they used more secular language and expressions, such as ‘indispensable tribute that we owe to Nature’, to discuss death. Other measures, such as requests for requiem masses (perpetual masses for the dead), bequests, offerings to the church, or even invocations of the Virgin Mary or average weight of funeral candles, all declined significantly.
What makes this event truly fascinating is the fact that such an important, early, and radical change affected the whole of society, not only a handful of philosophers, aristocratic elites, or a small section of the bourgeoisie. According to Francis Bacon, ‘where the cause is not known the effect cannot be produced, nature to be commanded must be obeyed’. The secularization of France meant that, for the first time, mankind – or, at least, an entire country – could command nature and break the chains of the Malthusian trap.
Methods of contraception beyond delayed marriage, ‘the fatal secrets unknown to any animal but man’, have long been known. The most famous, most readily available, and likely most effective method at the time, coitus interruptus, was even evoked in the Bible. However, these methods were not widely used, especially following the Counter-Reformation, when the Catholic Church, threatened by the spread of the Protestant Reformation, took ‘be fruitful and multiply’ seriously and the purpose of marriage became explicitly multiplicative.
With the loss of influence of the Church, the clergy could not oppose fertility controls anymore. In the eighteenth century, Casanova resorted to condoms (English riding coats, which were were made of linen or animal intestines, and weren’t too effective or widespread) and the enlightened elites and bourgeoisie of France practiced libertinage, les plaisirs de la petite oie (the pleasures of the little goose, to refer to mutual masturbation), and plenty of other pleasures alike. Ordinary people, liberated ‘from the teachings, the restrictions, and the yoke of the Catholic Church’, simply used coitus interruptus.
The regions that secularized experienced a much earlier decline in fertility than those that did not. The difference between Provence, a stronghold of dechristianization, and Brittany, a stronghold of Catholicism, is almost as large as that between France and England. According to the genealogical data, these places did not have lower fertility before: the fertility transition only took place after dechristianization. I also find that the effect persisted for generations, as persons born in secular places passed their secular values on to their children, even after moving to places with different institutional and cultural norms. This means that dechristianization was not only institutional but rather, and above all, cultural.
It is unclear why the Catholic Church’s influence waned so quickly and why France was the first country to secularize. Secularization took hold in regions that were by no means the richest areas at the time. Provence was a rural backwater of the Kingdom of France, speaking a different language and under different fiscal rules, suggesting that neither wealth nor institutions caused the decline in fertility. However, the Counter-Reformation, which was particularly powerful in France, is mentioned by historians on occasion. In fact, regions where Jansenism, a theological doctrine opposed by Jesuits and the Pope as heretical, was strongest in the eighteenth century secularized more. The same seems true for areas where the Catholic League was strongest in 1590, during the French wars of religion. Both facts imply that the French regions where the Counter-Reformation was strongest are those which secularized the most, suggesting that secularization might have been a backlash against religious powers closely connected to absolutism.
The consequences for France are astonishing. French historian Fernand Braudel argued that ‘the entire course of French history since then has been influenced by something that happened in the eighteenth century’, and asks, ‘did France cease to be a great power not, as is usually thought, on 15 June 1815 on the field of Waterloo, but well before that, during the reign of Louis XV when the natural birth-rate was interrupted?’
Yes, but this is not entirely accurate. While England was the cradle of the industrial revolution and developed with innovations and industrialization, France developed by challenging the authority of the Church and decreasing fertility and population growth, achieving growth in income per capita equivalent to that of England after 1760. Income per capita is, by definition, total income divided by population. In a nutshell, England increased the numerator while France limited the growth of the denominator – a radically different, but very effective, path of development. Maybe France is not (anymore) the China of Europe, but it is today a major economic power.
What can we learn from this? Today, the political and economic prospects of an empty planet are a worry for many, as more and more countries reach fertility rates below replacement levels. The population of China is projected to halve by 2100. The historical fertility transition in France shows that demographic decline – at least while still above replacement levels – does not necessarily spell society’s eternal doom. In particular, it could be a way for developing countries to adapt to climate change, by reducing the pressure of overpopulation and generating a ‘demographic dividend’, where the ratio of working-age to dependent population rises, raising average incomes and living standards. Just such a dividend has helped many developing countries escape the Malthusian trap, as it did for France in the eighteenth century.
Economic theory aims to explain the big contours of human behavior purely with reference to prices and incentives. No doubt these things are extraordinarily important. However, ignoring the effects of culture, and the fact that preferences and norms can change, is a mistake. The decline of Catholicism, and fertility, in eighteenth-century France turned it from a demographic powerhouse – the China of Europe – to merely a first-rank European power among several, but also allowed it to keep up with British living standards without an industrial revolution. Ideas have consequences.