To be clear, this is a transient problem. But it will take several decades for things to balance out, which could be problematic in the intervening period.
> It is unclear how a country stabilizes birth rates once they start falling, because no modern country has successfully done it.
One possibility is that they are continuing to fall because they just haven't reached equilibrium population yet. East Asian countries also seem (from my limited understanding) to have particularly bad social problems that further suppress birth rates, which Western countries don't have.
That's my understanding as well. I bet the 996 culture, 69-hour max workweeks, and constant rat race definitely don't help with this. Add to this a younger generation that thinks that they don't want to make the "sacrifices" that their parents did and would rather maximize their own quality of life (though I don't think this latter is just an Asian problem).
> But it will take several decades for things to balance out, which could be problematic in the intervening period
Corporations require continued growth to drive stock prices. How do you have growth when then population is shrinking? There are literally less people to buy gas, food, cars, iPhones, etc. Large investments designed to scale and handle capacity are now losing money, not in use, etc.
You handwave this like it's a simple thing, but it will shock the system and lead to massive problems. Perhaps it's necessary, but in the same way amputating a limb might be necessary -- painful and complicated.
It is unclear how a country stabilizes birth rates once they start falling, because no modern country has successfully done it.
Some countries supplement or offset their population losses with immigration, which comes with its own challenges.