[vlovich123]

In what world do you imagine a constant fertility rate over a 120 year period? In the 1950s everyone was concerned about overpopulation because it was so high. Now you’re concerned about a collapse because it’s low. It’s a silly fear because it’s a control system with a feedback loop. We’re just not used to seeing it oscillate because we’ve been in exponential growth for a long time, but exponential in nature must plateau and that’s what you’re seeing here.

Also you focus on individual countries and yet worldwide the population keeps increasing.

[zpeti]

You are making a big assumption about it being cyclical. Never in history have we had contraception, it's a huge change to human behaviour. It's not at all obvious that women actually want more than 1.5 children on average in the west.

We also have tinder etc and a bunch of other changes that are HUGE in terms of culture.

I'm not saying any of these are bad, and there's not way we are going back to no contraceptives. But to ignore the effects of these, ESPECIALLY as birth rates are trending down EVERYWHERE, is pushing your head in the sand.

You are making a lot of assumptions, and as my example shows, if your assumptions are wrong for say ~50 years, you've already made a huge dent in your populations makeup.