I agree that immigration is a big part of fixing this.
I think if the population (replacement rate )declines too swiftly, you have a lot of old people and few young people. At some point it become exponentially harder to even keep your last generation’s replacement rate, and you have spiraling population decline. See South Korea for the Speedrun.
If Japan steadily declines to 80M it could be fine. If Japan goes to 80M in a generation, that’s very very bad for the chances of there being any Japanese people left in a few more generations
I agree that immigration is a big part of fixing this.
I think if the population (replacement rate )declines too swiftly, you have a lot of old people and few young people. At some point it become exponentially harder to even keep your last generation’s replacement rate, and you have spiraling population decline. See South Korea for the Speedrun.
If Japan steadily declines to 80M it could be fine. If Japan goes to 80M in a generation, that’s very very bad for the chances of there being any Japanese people left in a few more generations