The countries that do pay for it don’t have significantly higher fertility rates.

I’d say there’s an elephant in the room: Childbirth sucks. If you want women to willingly subject themselves to that, you need either a culture that virtually requires it-

And I want to take a moment to emphasise that I don’t like nor want this solution, and would fight anyone who tries for it.

-or you need to pay them well above the actual economic cost of rearing a child, because the process itself is strongly negative. Yes, having a child itself can be great. Eventually, several years in, when they start to become a person.

That’s true, but if you ask any of the women I know, they’ll tell you they’re perfectly happy to keep it at one.

That’s in Norway, by the way, so not one of those countries where you get zero support.

What I find interesting is that, it really seems that the opposite is true.

My great-grandparents (and their entire ancestry that I can trace, all the way back to 1807) were punishingly, desperately: poor.

Yet, it seems they averaged a heck of a lot more children than me, or my contemporaries. And their children largely lived to be adults with only a few minor exceptions.

The adults themselves didn't seem to live long though, most records of marriages I have are for 17-18 year olds who were already orphans.

This has always been true. We have talked about the costs of raising children forever.

What is different now, is twofold: 1. Bigger financial impact of having a child, both through less government support, and because more women are working. This combined means that to have a child, often, one of the parents needs to stop working, which severely impacts SoL. 2. Less social impact of not having a child. It is far more common to not have children than it used to be, and so it becomes much more of a choice as to whether to make that SoL sacrifice or not.

Are they paying for it in the countries with high birth rates? I don't think so...

Yes. Societies have been using their women's children as a positive externality for generations, but now the logic of capitalism and societal freedom has caught up, and now societies would rather collapse than support women and families economically for the work of childrearing.

I think Derek Thompson is a hack. Based on his media appearances from the Abundance tour, he seems to be very libertarian but in a (neo-)liberal space that pays his bills.