>which is the central thesis here

No, not exactly. We're dealing with a historical confluence of long term changes in humanity. Before 1900 or so and some people had a lot of kids survive and others had a lot of kids die. The population rate increased very slowly, and not from a lack of trying. Then around the time I stated people figured out germs were real, chlorine in water was good, and washing ones hands was a swell idea. The population exploded.

Then you couple this with the technological revolution and the necessity of training huge amounts of the population for specialists jobs if they want to make a living and suddenly a boat load of kids doesn't make any sense at all. And it's getting to the point of the squeeze that having any kids doesn't make a lot of sense for a lot of people.