Fertility rate dropped over 50% within 10 years in Argentina

Because children are expensive, in time, fiat, and opportunity cost while the freedom of being childfree is free if you choose to have less or no children. Social media allows for the socialization of these ideas at speed versus historical transmission rate of culture and social norms. This is covered most robustly in my Birthgap video citation above, additional citation below (by the same author as the tweet that is this post).

Terra Incognita: The Economics of a Shrinking World [pdf] - https://news.ycombinator.com/item?id=49352811 - August 2026

> "As of 2026, humanity is likely below replacement fertility. That has never happened before, not in wars or pandemics. But the real surprise is that the fall has been concentrated in low- and middle-income countries and among poorer and less educated women. We fit a single-factor model to 236 countries since 1950: the common component peaked in 1978, and what drives fertility down today are country-specific trends, 219 of them negative and not one leveling off. None of the commonly cited mechanisms can account for this pattern, so we offer a conjecture: modernity itself, which makes a third child expensive and childlessness cheap. Children come in integers, so it takes very little to move a cohort’s fertility rate from 1.8 to 1.3. And nothing in an economy pushes fertility back to 2.1. We close with the main economic consequences, in particular slow growth."

> There has to be a backstop somewhere otherwise you get infinite regress.

In summary, the global population boom happened because women were not educated and empowered to assert their reproductive choices. They are now. We are currently performing neutral fertility rate discovery via who does and does not choose to have children when it is a choice, versus when it is not a choice or forgone conclusion. A byproduct of this was economic growth, which is coming to an end, and will not repeat in our lifetimes based on demographic trends and trajectories.

South Korea’s problem is sexism, not space. My citation above speaks to this in depth.

Correlation and causation

Not everything is capitalism.

Mass forced sterilization, sex-selective abortion and infanticide, 13 million heihaizi (unregistered children = "illegals" in their homeland), ongoing repercussions in the skewed gender ratio and demographic cliff / "4-2-1" families...

And all for supposedly controlling a birth rate that had already fallen to 2.7 by the time it was implemented. And modern scholarship suggests the typical effects of economic development would have kept it running down steadily without all the costs incurred by an unevenly enforced law, given what happened everywhere else that had no birth-control policies.

The whole world seemed to buy into the narrative at the time, but history has shown it to be an example of misguided authoritarian foot-gun akin to the Four Pests campaign.

But we are, I think, far more thoroughly bombarded with news about how doomed everything is than in prior generations. 24 hour news is itself pretty new, and social media is more pervasive than it ever was.

It’s the inflation itself, not the cost of living. Inflation does weird things sociologically and psychologically, you’re messing with the fabric of human economic relations which is implicated in status hierarchies and assortative mating

Climate crisis and economic crisis both prevent people from wanting kids.

Yes. About 20 years ago, I was to a family reunion, with (almost) all of the descendants of my maternal grandmother's parents. We were over a hundred: mmm and mmf had 9 children, who all lived, all got married and all had at least two children, many had more. The next generation did well too.

Many years later I got into family history, and looked into what happened to mmm's sister, who emigrated to the US. Turns out she had six children, but only four lived up, no one had more than two children, and her last descendant died during covid. It's technically possible there are descendants of course, but then they're "off the books" and would have been unknown to that last guy who died.

mmm's three other siblings too have no descendants - one moved to US, fought in WW1 and died a bachelor at over 100, the two others died shortly after age 18, both in drowning accidents.

So, even back when fertility was much higher, just because you had children and grandchildren didn't mean you'd have descendants a few generations further down.