Most people aren't thinking about the ROI of their kids, that ironically is a pretty modern twist.

Birth Control is way, overwhelmingly the #1 issue, so far ahead of anything else. Condoms and 'the pill' are a very new phenom. Imagine before them, when every sexual act had a pretty high change of pregnancy. And then it's easy to understand how sex<->marriage<->family are so deeply intertwined in pretty much everywhere. 'Sexually active' basically guarantees children, children need stability, so it's 'nuclear family' or bust for the most part, before the pill. An enormous amount of social conditioning is baked into this.

'Working for corporations' is better than 'working in a factory, mine, or on land you don't own' ie serfdom, which would have been the default for most of our ancestors in one way or another.

Undoubtedly, the 'thing we cannot say in public' is that double-working families has had a double effect on the family 1) less time and 2) more acerbically - the cost of living goes up, particularly for property, forcing everyone else into the same 'two workers or risk being be poor' trap.

Playing with the reproductive system (I mean social system, not so much physicality), is really, really dangerous, as I don't think our individual intentions are all that positive - but the silver lining is that the world does have quite a bit of people, and that in many places, we do need to have less kids.

Remember we're living a lot longer now as well.

So at least for the moment, if India and Nigeria can get a grip on fertility ... it has upsides.

The real challenge, and scary things is what this will mean longer term. Once Japan drops to a certain point, will they level out? Or expire?

Hopefully we can work it out.