I'm not lol. That's the point. Even if Japan or South Korea had full reverse right from this instant, a collapse that will last decades is inevitable. That's the consequence of low and further declining fertility rates for decades. The table has already been set.

Yes, a 'collapse' is inevitable. But you seem to be suggesting that it will go on 'collapsing', is that not correct? (Please correct me if my assumption is wrong.) Populations do not keep collapsing to zero; at some point the decline is reversed.

And a population 'collapse' is not necessarily bad for a country or a region in the long term. Indeed it can be rejuvenating in the long term. Europe suffered a massive population 'collapse' after the Black Death pandemics. This had the long term effect of making peasants' labour more valuable which ultimately led to the Industrial Revolution and the rise of a Middle Class.

I never said anything about collapsing to zero.

And raw population numbers are the least of the problems here. The comparison to the Black Death is rather silly.

> The comparison to the Black Death is rather silly.

Why? It's a very well explored and prominent example of a population 'collapse' leading to long term rejuvenation (and innovation).

I'm not pretending that some of the short term to medium term consequences of a population 'collapse' (I keep putting it in quotes because it's your word and I think it's too emotive a word) won't be dire. But at some point a population has to go through a period of decline. We see this all the time in the natural world. People who don't want to have any periods of decline and go all Pollyannish with emotive talk of 'collapse' and worse for any period of population decline seem to be stuck in a fantasy world, in my opinion. Not the real world, where, to slightly belabour a point, animal populations go through cycles of growth and decline, repeatedly.

Sadly, their mathematical assumptions are actually very reasonable and conservative. They're not saying "this exponential trend will continue", they're saying "what happens in 30 years to South Korea if the current state continues?"

And the answer is that there will be something like two 80 yr olds for every 30 yr old.