There is ZERO evidence that's the case. In fact all evidence points to the opposite. The more money people have the less likely they are to have children.

I'm not suggesting that we should therefore lower people's incomes. Only suggesting that the idea that his has anything do with lacking economic opportunity has zero basis in fact.

The richer a country gets, the less kids they have, period.

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follow up: According to this

https://en.wikipedia.org/wiki/Income_and_fertility

birth rates do rise at some level of income but not enough to cover deaths.

Here's some other charts to look at

https://ourworldindata.org/fertility-rate

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To put in another way, let's wonder if we lived in a post scarcity society and everyone had all they needed and more. Would the birth rate explode? Would it go up a bunch? Would it hit the replacement level? I suppose it's all speculation but my reading of the data it is would not hit the replacement level.

Basically, for whatever reason, people that are well educated and well off want children less than those that don't for whatever reason.