Thread by @gguillaumeblanc

Why did the demographic transition, essential condition for development, took hold in 🇫🇷 more than 100 years earlier than in any other country?

My #JMP uses crowdsourced genealogies to comprehensively document the decline in fertility & identify its origins for the first time 🧵

Why does it matter? Without an escape from the Malthusian trap, no sustained growth is possible

👇👇 The hockey stick graph! 🏒🏒

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 🤔

What caused this event is still one of the "big questions of history" (Darnton, 1978) because

1️⃣ It challenges most explanations: 🇫🇷 was a poor, illiterate, rural country

2️⃣ Data limitations: only a few case studies in rural places—no census or comprehensive data at the time 🤷🏻‍♂️

👨🏻‍🏫⚡️ My JMP leverages crowdsourced genealogical data from publicly available trees on geni. com to comprehensively document the demographic transition in 🇫🇷

➡️ The decline in fertility took hold in the 1760s, mind-blowingly early and slightly earlier than previously thought 🤯

Of course, I carefully evaluate selection and compare observables in the genealogies to the best available representative data and census when available. There is a >95% correlation with representative series! 🙀

- Urbanization and life expectancy 👇

- Fertility 👇

Only available data to compare genealogies to

1️⃣ census after 1851 (🇫🇷 & 🇬🇧) most comprehensive

2️⃣ family reconstitution in small N of rural places (🇫🇷 & 🇬🇧) very selected

3️⃣ extraction of aggregate statistics in large N of places (dashed, only 🇬🇧) much better

So, the decline in fertility took place exceptionally early. But why? 🤔

My hypothesis: secularization! 🌊

In aggregate-level evidence, relying on the work of historians (esp. M. Vovelle), I document an important process of secularization that took hold at the same time in 🇫🇷

➡️ With dechristianization (in the mid-18th century!) the Catholic Church lost influence and could not oppose fertility control—coitus interruptus—anymore 🛏 ❌⛔️ ⛪️

Time series of secularization using data on wills 👇

In the second part of the paper, I document a particularly strong and robust cross-sectional correlation between secularization and fertility

Both 1️⃣ at the department level using census data (obviously with censoring), and 2️⃣ at the individual level using the genealogies

In line with the aggregate-level evidence, I estimate that a full secularization 1️⃣ delays the transition by more than a century, and 2️⃣ decreases fertility by more than one child per woman

Then, using distribution regressions with the individual-level genealogical data, I show that secularization affected most the largest families 👇

(see this wonderful thread )

Finally, using the genealogies allows me to account for unobserved institutional and geographical factors with a range of standard strategies applied to this setting ⬇️

Some (not me 😇) would even say to establish causality 👀

1️⃣ I show that secular places did not have greater fertility before! (~ DiD)

2️⃣ I study second-generation migrants in the genealogies by tracing migration between districts in France at the time (❗️) —> secularization captures persistent cultural norms and beliefs

You can download the paper here 🔗 bit.ly/BlancJMP2

I hope this 🧵 has convinced you that this event was a turning point in human history. Thanks for your attention!

To conclude, some more anecdotes/implications:

1️⃣ Had population growth in 🇫🇷 followed 🇬🇧's, there would be ~250M inhabitants in 🇫🇷 today!

2️⃣ Spolaore & Wacziarg show that the limitations of fertility adopted in 🇫🇷 spread in Europe along linguistic/cultural lines —> 🏒🏒

3️⃣ Although England was the cradle of the Industrial Revolution: *SAME* rate of growth of real GDP per capita in 🇫🇷 and 🇬🇧 after 1760 👇

- 🇬🇧: let's get richer by producing more and inventing stuff
- 🇫🇷: hold my 🍷 let's have less kids 😏