Although we generally attribute low birth rates in the US to “degeneracy,” birth rates are even lower among those Asian societies that are more “traditional” in character. Also, the divorce laws, and other such factors, are different than in the US, and generally more family-friendly. What’s going on?
The first, and obvious, thing is that the married birth rate in the US is about the same as in Asia. About 40% of children in the US are from unmarried mothers, while in Asia the figure is more like 3%. Multiply the present US birth rate (1.78 tfr) by 60% (married mothers), and you get an Asian-like figure (1.06 tfr). (South Korea recently posted a total fertility rate of 0.78.)
The idea of the stay-at-home Mom is more common in Asia, such as Korea, Japan, Taiwan or Singapore. This is generally thought of as high status. However, there has nevertheless been a creeping feminism. Women go to college, and then get jobs. This itself chews up a lot of time and energy, and also, does not press women toward marriage since they can live alone. We also have the factor that women don’t want to marry men that make less than they do, or even the same amount.
We then have the factor of extreme K-selection tendencies, especially in Asia, but also among typical upper-middle-class families in the US. All of childhood becomes a constant struggle to “achieve” according to some metric, although nobody seems to be getting much of an education in this process, or even developing meaningful hobbies or other interests. This struggle for “achievement” is exhausting for parents and children alike. As these children become parents themselves, they do not want to put their children through this process, nor undertake the parental responsibilities involved either. Probably, they should just give it up, relax, and find something better to do. But, instead, I think that there is a tendency to think that, if a child doesn’t “achieve” according to this process, there isn’t much point in doing the whole thing at all. Who wants to plan on failure in advance?
All this activity for “achievement” takes enormities of time, energy and effort. It is a daunting prospect for one child, and difficult to imagine even for two children, especially if the wife is also working. Three seems like fantasy. But, in the past, even the wealthy adopted more of an R-Selection process, or the more the merrier. Even with all the advantages of wealth, you would get some good kids and some not so good. Look at Pride and Prejudice for example. Mr. Bennett had five daughters, all raised with roughly the same care. Two were excellent, one was rotten, and two were middling. That’s why you had five.
Related to this is the extreme cost of all these things. With a stay-at-home Mom, daycare costs are not an issue. However, that also means that the family must live within a lower income. College costs are daunting for even one child, and more than two seems like total fantasy. In the US, working Moms face daycare costs, and $1000 a month is common. $2000 a month is common in some cities. That consumes a lot of after-tax income for one working Mom, and becomes ridiculous at three. The way out of all this is, of course, staying at home, and homeschooling, since then you have the private school/public school issue.
Retirement is an interesting issue. Old people need care, especially as they get over 75 — and, with better medicine, a lot of people are reaching those ages, rather than dying from some other factor before that time. Traditionally, children were a retirement plan. But today, both children and elderly reject the idea of living with their children in retirement. Money is their retirement plan; and with more children, they may feel there is less money.