[zpeti]

The reason this isn't a doomer Elon Musk theory is that the numbers are very counter intuitive. Add to this the fact that our average age is also rising, hiding the worrying signs even more.

Imagine we have a society with 100 people with a fertility rate of 1, that give birth at 20 and die at 80. Here is how that looks:

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Year 0: 100 newborns (Population is actually 300 at this point)

Year 20: 100 twenties, 50 newborns

Year 40: 100 forties, 50 twenties, 25 newborns Year 60: 100 sixties, 50 forties, 25 twenties, 12 newborns

Year 80: 50 sixties, 25 forties, 12 twenties, 6 newborns

Year 100: 25 sixties, 12 forties, 6 twenties, 3 newborns

Year 120: 12 sixties, 6 forties, 3 twenties, 1 newborn

within 120 years you've gone from 300 people to 22 people

Korea is worse than this. Japan is close, Europe is getting close. A birth rate of 1 is not impossible worldwide soon.

[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.