That is an interesting hypothesis. Zeihan wrote that it is/was the industrialization of agriculture combined with child labor laws that shifted children from as

That is an interesting hypothesis. Zeihan wrote that it is/was the industrialization of agriculture combined with child labor laws that shifted children from assets to liabilities resulting in fewer births. The book presents fairly compelling data to support the correlation, but population density could be a confounding factor. I grew up in a (very) rural area and the people I knew even from the nearest town had far fewer children than my great grandparents did. Tractors became cheaper than 12 kids. And I guess even without child labor laws, there aren't a lot of modern jobs kids could do I think.