Robin Hanson on Declining Fertility

Since we’ve both been writing a lot about the topic recently, Robin Hanson invited me to sit down and chat with him about the global fertility decline and prospects for depopulation. We recorded a conversation this week, Robin posted it on YouTube, and I’m sharing it with my readers on this site.

Robin and I agreed on many things: the woefully underappreciated importance of this development, the main underlying factors, the threat to technological innovation and economic growth, and the threat to liberal values. Here, though, I’ll say a few words on a couple of points of difference.

First of all, Robin is convinced that fertility decline was a frequent driver of civilizational decline in the pre-modern world. The cyclical story goes something like this: a new polity rises and expands, grows richer and more complex, and the growing affluence triggers a decline in fertility, leading to population loss and a gradual unwinding of the division of labor and social complexity. If this is true, then that suggests that there is strong, perhaps irresistible historical momentum behind contemporary demographic decline: humanity has played this movie many times before.

This story of ancient fertility declines is pretty much the opposite of the Malthusian conventional wisdom that I’ve always assumed to be true. To be sure, civilizational declines have been associated with sharp drops in population, but my assumption has been that the causality ran from civilizational health to demography rather than vice versa. That is, after civilizations peak, various forms of decline set in: declining income from plunder and rising costs of administration, leading to tax increases, leading to more unrest in the provinces, leading to higher military expenditures and higher taxes, in a downward spiral. As imperial control degrades, trade suffers, the division of labor unravels, and the shrinking economy can no longer support the population, and thus Malthusian dynamics kick in to reduce numbers.

I’d like to read more about this, but there is at least some evidence for ancient demographic transitions. And there is contemporary documentary evidence of declining marriage and birth rates among the elites in Greece and Rome. I’m quite open to the idea that elites could successfully control fertility; I’m much more skeptical that society-wide birth control was engaged in effectively enough to drive down birth rates. Anyway, I’m interested in learning more.

Second, Robin is pessimistic about the possibility of spontaneous reversals in fertility because of the multiplicity and robustness of the factors underlying the current decline. Because declining fertility is associated with a number of the most universal trends of modern social development — urbanization, rising wealth, rising economic opportunities for women, declining religiosity, access to reliable contraception — ongoing decline in fertility seems massively overdetermined.

I didn’t get into this during our talk, but afterward I started thinking that maybe Robin’s mental model is oversimplified — and that consequently his pessimism may be excessive. Maybe fertility decline isn’t this monolithic trend that started in France in the 18th century and gradually covered the planet; maybe there have been important differences in the main drivers of fertility decline over time. Some demographers now distinguish between the original “demographic transition” — which took societies from high birth and death rates to low ones — and a “second demographic transition” in which already low-fertility societies plunge below replacement levels. Many of the features of contemporary fertility decline — rising ages for marriage and children, declining marriage rates, and sub-replacement fertility — are novel, which suggests that the factors involved have shifted. Instead of a cumulative process in which various master trends of modernity combine to exert a steadily increasing downward pressure on fertility, maybe the most important drivers of sub-replacement fertility are less deep-seated — and therefore more easily reversible — than the factors that propelled the transition from big to small families.

If you dig into the details of the countries today with the lowest fertility, what pops out is a breakdown in the mating market caused by asynchronous cultural change. Check out this fascinating article on South Korea’s fertility freefall: sharply diverging expectations and rising resentment and animosity now mar the relationship between men and women in Korean society. Women can now choose whether to marry, and choose whether to have children — and they’re having a tough time finding suitable prospective husbands and co-parents. There are cultural lags in both directions: many men aren’t reconciled to women’s expanded freedoms and choices, while many women cling to hypergamy despite its roots in women’s subjected status. Perhaps, then, sub-replacement fertility isn’t an inevitable result of the master trends of modernity; maybe it’s a temporary effect of lagging cultural adaptation to new realities. Accordingly, there’s at least some basis to hope that the specific conditions driving us toward depopulation could prove reversible over time.