Third of Japan's 18-year-olds women may never have children: study

It was different in premodern cultures.

Back then a child could be contributing positively to the farm in a few years and don't need a lot of training because they want to do the same things people around them are doing. Power tools require a certain level of maturity and judgement, my son was able to pick up a hoe when he was a toddler but our tractor has a weight switch in the seat and we had to make him wear a backpack with weights in it to drive it for the first time. (We even had a small adult woman living at the farm who was too light to trigger the switch.)

(My son didn't make a positive contribution, however, to the family business, a riding academy, until his mid teens. Until then he was always a little resentful of the horses since they were the reason his mom was often not around. Then there was that day he was roughhousing in the barn, a behavior the horses can find a little offputting, and he realized that one horse was taking an interest in his activity and that got him to recognize the social intelligence of horses... Before then we were worried about who would cut the hay when the farmer who does it retired, now we are not.)

Contrast that to the current day where children are an economic cost up to high school graduation if not college, grad school, etc. and whether or not kids go to college they often seem to have an adolescence that extends into the mid 20's.

Back in the day a huge family was your retirement, now we have social security and stocks and bonds (which are still dependent on demographics.)

I've known a few people who have had huge families (10+ kids) in the modern day and they have a very different mindset. It's not as much work and cost once you reach a certain point as the older kids help take care of the younger kids and that gets around the "parents are not gods" problem that are talked about in

https://www.amazon.com/Parent-Effectiveness-Training-Respons...

also there are a lot of hand-me-downs and other synergies. (Although my dad was quite bitter about getting hand-me-downs and sharing the bed with his brothers...)

A lot of the increased "standard of living" is not the things we think are optional (and "consumption") like the iPhone and the vacations, but rather the things that we think are necessary (and even "an investment") such as health care, a house in an expensive neighborhood with a good school district, etc. Remember this Liz Warren classic

https://www.amazon.com/Two-Income-Trap-Middle-Class-Parents-...

Raising kids is difficult and time consuming. As people gain more opportunities to do other things than raise kids they chose to do those other things instead. It's an opportunity cost issue, not a literal cost issue. That's why the birth rates goes down rather than up as you climb income percentiles. People with more money have more opportunities.

The only real force to counteract that is cultural/social pressure to raise kids which has also fallen off pretty hard. It might be less obvious to younger people or people with younger parents but having kids was much less of a "decision" for couples not that many decades ago and was much more just an assumed fact. If you didn't, people assumed there was something wrong with you.

This is a problem that'll solve itself eventually; the desire to have children is to some degree inheritable, so the people with genes that make them still likely to have children in modern society will outbreed the people with genes that make them unlikely to have children in modern society. Similarly the cultures that make people more likely to have children will outspread those that make people less likely to have children, so maybe in a few centuries the Amish, Orthodox Jews and Muslims will rule the earth.

There is a convergence of reasons, and Japan is only ahead of the curve.

People who have been raised as a single child are unlikely to have more than one children, this is simple pattern reproduction.

The cost issue is mostly related to cost of space, with today standards we need one more room per child, not everyone can afford that.

Culturally, the pressure on girls and young women has relaxed tremendously, education and financial freedom have a very measurable effect on natality.

Overall, I don't think this is a bad thing. We can adapt.

Also, population is a huge variable in energy/resources/pollution.

Even when it's your own house that is on fire?