Well, (1) was implemented, (2) wasn't.

If we were to constrain ourselves to conditions in Southern California

FYI the SF Bay Area is in Northern California.

[next quote is reformatted so that I can make it a quote]

This can be interpreted in two ways: wealthier people see children as higher cost and elect not to have children because of the costs; or wealthier people are not under as much economic pressure so have fewer children because they can afford to get away with it. At the margin, both of these things are going on at the same time.

Glad to see we agree - and again, the important point for my argument isn't whether most of existing low fertility can be attributed to the existing cost of kids, but whether adding extra cost per kid will reduce the number of kids (as the law of demand predicts).

The capacity to home-school is roughly all-or-nothing. Home-schooling one kid immediately scales to home-schooling all your kids.

I'm sure this can't be exactly right, but I do think that the low marginal cost of home-schooling was something I was missing.

This means that, for a given family, you essentially chose between having kids and home-schooling all of them (expected-cause of home-schooling doesn't scale with number of children) or having no kids (maximum social penalty). Electing for "no kids" seems like a really undesirable trade-off for most people.

I continue to think that you aren't thinking on the margin, or making some related error (perhaps in understanding what I'm saying). Electing for no kids isn't going to become more costly, so if you make having kids more costly, then you'll get fewer of them than you otherwise would, as the people who were just leaning towards having kids (due to idiosyncratically low desire to have kids/high cost to have kids) start to lean away from the plan.

This leads me to believe that, compared to other pressures against having kids, stigmas against home-schooling will have an unusually low marginal effect.

(I assume you meant pressure in favour of home-schooling?) Please note that I never said it had a high effect relative to other things: merely that the effect existed and was large and negative enough to make it worthwhile for homeschooling advocates to change course.

Why would having such an explanation make one less "impressed by the obvious political and free speech ramifications"?

I wouldn't read too much into the "forever". Later in the post:

I like economic explanations for behavior. You don't need politics or morality, just good old self-interest. That's why I became an economist. At least they are acting "as if" this is the motivation, which for explaining behavior is all that matters. That doesn't make the actions any less coercive, nor the grab of power over academic appointments any less revolutionary. [emphasis DanielFilan's]

The follow-up post has a public-choice-esque model of what's going on that I think is plausible:

I started this series impressed by the obvious political and free speech ramifications. There is a much simpler economic explanation however. As the quotes from the UC system make clear, the central requirement of the diversity statements is to document past active participation in, and require future approval and participation in all the programs produced by the diversity staff...

Some quotes from the UC post, what gets you a good score

Participation in workshops and activities that help build multicultural competencies and create inclusive climates....Supporting student organizations that serve underrepresented groups....Participation with professional or scientific associations or meetings that aim to increase diversity or address the needs of underrepresented students, staff, or faculty. Serving on university or college committees related to equity and inclusion... Clear and detailed ideas for what existing programs they would get involved with

Universities have created a huge diversity equity and inclusion staff. The faculty regard this sort of thing with something in between horror and annoyance. Even super left wing faculty, especially in the sciences, want to hire good people and get back to work without too many diversity activities. They'll happily look hard and promote "diverse" candidates informally, but don't waste their time.

The diversity staff have a problem. By forcing these statements, and the staff ability to grade them before anyone gets a job, and to follow up when you ask for a raise or promotion, they create a great device to coerce participation in and support of their programs, their ever increasing staff, their budgets, their jobs. Disagree and you're branded a racist!

If the old arguments were sound, why would researchers shift their arguments in order to make the case that AI posed a risk?

I get the sense that a lot of it is different people writing about it rather than people changing their minds.

If anybody has any questions about this, I'd be happy to answer as a Metaculus community moderator!

My sense is that on average, more population means more growth (see this study on the question). But certainly at some point probably you run out of ideas for how to make material more valuable and growth just becomes making more people with the same consumption per capita.

Whether we're in a downward-sloping portion of the curve, and whether it slopes up again in the next few generations, are both debatable. And they should be debated.

I find this comment kind of irksome, because (a) neither I nor anybody else said that they weren't proper subjects for debate and (b) you've exhorted debate on the topic but haven't contributed anything other than the theoretical possibility that the effect could go the other way. So I see this as trying to advance some kind of point illegitimately. If you make another such comment that I find irksome in the same way, I'll delete it, as per my commenting guidelines.

One factor here that is big in my mind: I expect per-capita wealth to be lower in worlds with lower populations, since fewer people means fewer ideas that enrich everyone. I think that this makes 2 go in the opposite direction, but it's not obvious to me what it does for 1.