Why were the French first to have fewer children? Secularisation

I know the rows over fish and migration mean we’re not talking to the French these days, but pondering their history is still allowed.

A huge historical puzzle is why France, from the 1760s, underwent the demographic transition to lower fertility rates a century before the rest of Europe. It’s a puzzle because economists usually argue that fertility declines are driven by technological progress, making human capital more useful and raising the cost of kids. But pre-revolution France was backwards on most development measures, with half the literacy of England and Wales.

An interesting paper crowdsources family trees to provide the answer: secularisation. Dechristianisation saw the Roman Catholic church lose influence in 18th-century France, with religious giving falling and references to God disappearing from wills. The loosening of traditional religious moral constraints also led to the wider use of contraception (of the coitus interruptus kind).

The author shows that areas where priests stayed loyally Catholic during the French Revolution (ie where secularisation had made less progress) had much smaller falls in fertility. Religious, rather than economic, change drove the demographic transition, but it had big economic consequences: falling fertility is a prerequisite for rising living standards (or progress gets eaten up by population growth). That’s why French GDP per capita kept pace with England despite the industrial revolutiontaking place on this side of the Channel. For the French, the story was less church, fewer kids, higher incomes.

• Torsten Bell is chief executive of the Resolution Foundation. Read more at resolutionfoundation.org