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Comment by grej | Hacker News Reader

South Korea was among the poorest countries in the world - poorer than many countries in Sub-Saharan Africa as recently as the 1960s. Withing a single lifetime they transformed themselves into one of the most advanced developed economies on the planet with a madman (mad men) on their doorstep.

It’s natural that that kind of change will have some massive societal implications, many of which they are still sorting out.

Their birth rate is something that will require immense attention and work to begin to correct, but it’s worth noting what they’ve accomplished in getting to a place where they can afford to worry about that as one of their primary concerns.

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> it’s worth noting what they’ve accomplished in getting to a place where they can afford to worry about that as one of their primary concerns

It's probably also worth noting the long history of military dictatorships, murderous suppression of worker rights, massive ongoing corruption (including a literal cult controlling the government until 2016) and the highest suicide rate in the world. Reducing the story to just economies is truly narrow minded.

And yet, despite all that, the median person is much, much better off than prior to all the economic development.

You can say the same things, or even worse, about many countries in the same time frame — China, Indonesia, South Africa, Brazil, Chile. South Korea both achieved economy miracle, and transformed itself into a solid democracy, better than any of the others

It's easy to illustrate the impact of fertility rates by model, and it's far more rapid/severe than I think most realize. A fertility rate of "N" means that the next younger generation will be N/2 times as large. So, a fertility rate of 2 means no change, while a fertility rate of 4 would result in an exponential doubling. How about 0.7? We can create a population distribution of this easily enough because we know how big each generation will be relative to the one after it. Assume each generation is 20 years (if its longer - things look even worse). We end up with, for instance:

===

1000 eighty year olds, 350 sixty year olds, 122 forty year olds, 42 twenty year olds, 15 newborns.

===

So you have a working age population of ~300 people working to support a population of 1529. You have a median age of 80, and an average age of 70. Think about the pressure on hospital, healthcare, and any sort of pension or other programs. Those 300 people need to not only man all of these jobs, but also somehow keep the entire economy from collapsing. I mean it's just not going to work.

And then of course your population will be declining catastrophically quickly. The ~20 years during which those 1000 eighty year olds die will result in a population decline of 65%. Yet that's no salvation because the ratio of age distributions won't change at all, unless fertility rates do. You'll end up in the exact same position, continuing to lose 65% of your population each 20 years to come.

In other countries automation proceeds at a geometric rate. So the idea of 'working to support' means far, far less.

We can hope that helps in the long run.

That's true. I ran a simple model a few years back. I expected my population to last for a few centuries at reproduction rate like 1.5, but they all died super quickly after an initial bulge.

Next 30 years are going to be a huge surprise for the population of all developed countries that they has successfully shrugged off till now.

Even worse, it's N/2.1 rather than N/2 due to pre-child-bearing-age mortality.

OTOH, obviously 1000 people aren't going to be alive at the age of 80. In Korea life expectancy is 83, but if it was 80 then we'd have 500 people alive at the age of 80, not 1000.

It'd be interesting to redo your numbers with an actuarial table.

OK, redone with the US actuarial table.

    age fraction alive
    0 1
    15 0.99156
    30 0.96994
    45 0.92732
    60 0.8273
    75 0.57758
    90 0.1437
    105 0.0034

Average age of mother at birth is 29.6 according to Google, so using 30 year generations.

For TFR of 0.7, generation sizes are 1000, 339.5, 114.3, 38.5 and 12.9.

At Y+105, populations are:

    Age    Pop
    15     38.1
    45     101.9
    75     144.7
    105    3.4

Contrast with US level TFR of 1.85:

generation sizes: 1000, 897, 798, 710, 631

Current world TFR of 2.3:

generation sizes: 1000, 1115, 1234, 1364, 1509

    Age    Pop
    15     1352
    45     1100
    75     475
    105    3.4

correct?

There are reasons from an economical point of view why a shrinking population isn't great. So they may see it as a problem that needs correcting.

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