> I have loads of family in South Korea, a country in near terminal population decline, and the reason I've always heard is "it's expensive to raise a child". But the real reason is, it's expensive to train a child to get into a top-3 university. Raising a child to adulthood is possible even in abject poverty.

Isn't the fact that mothers are expected to drop their career and 100% focus on their children also a factor? Women instead decide not to have babies at all so they can have a career of their own.