Comment by somenameforme | Hacker News Reader

Comment by somenameforme | Hacker News Reader

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There's an interesting aspect of fertility rate that most don't know. They also determine the exact age ratios within a society! Imagine a population has a global fertility rate of 1 (and in Singapore it's even lower, though not globally - yet). That means each successive generation is half as large as the one prior. And we can approximate the age of fertility as between 20 and 40. So now let's start with 1 newborn and we can work backwards from there.

---

1 new born ->

2 20-40 year olds ->

4 40-60 year olds ->

8 60-80 year olds ->

16? 80-100 year olds

---

Just ignoring the 80-100 year olds, we end up in a scenario where you have 6 people in the working age for every 8 people of retirement age. And if life expectancy inches up, then it may be closer to 6 working age people for every 16+ retirees.

You can see this visibly playing out in Singapore right now with their population pyramid [1]. They had a nice solid pyramid in the past, so you end up with a very healthy economy and society - lots of young people for relatively fewer older people. But as fertility rates declined you can see it start to flip, so right now it looks a bit like a vase, and in the future it will be an upside down pyramid.

So basically as the old folks move on, they are replaced by even more old folks. And this never really stops until we return to being societies that are having enough children to sustain ourselves.

[1] - https://en.wikipedia.org/wiki/Demographics_of_Singapore#/med...

Indeed. And this burden of a top heavy population pyramid is a major reason for not having [more] kids - a vicious circle, which, if left to continue, will result in humanity simply evaporating.

A pretty depressing place, with whole towns and cities abandoned, as the dwindling population huddles closer together. Not just geography though, there would also be a retreat in the arts, sciences, etc as there are simply not enough people to maintain let alone advance these endeavours. Life would be about eking the last out of what was left over from the 'glory days', a sort of slow motion apocalypse.

I really am not following your logic here at all. You're precisely describing what happens from not having more kids.

Thankfully there's infinite people from other countries who can migrate freely and replace the aging population, right?

(Serious question)

Where do you propose regularly finding hundreds of millions of skilled English speakers of similar values who are interested in permanently migrating to what will be countries clearly in decline?

India, that's where everyone else gets them. People are just economic units

Even India's fertility rate is now below replacement, and they're increasingly actively working to turn the tide on their brain drain. And India's economy is both already massive and growing quite rapidly. At current trends they'll pass the US within a decade or two. They certainly aren't just this long term sustainable pool of people to draw from.

In my observation, there are a lot of unaccounted for and unintended issues that can arise from this.

Where I live, we are going through a lot of this right now (98+% of population growth is from immigration).

Immigrants have more kids than the non-immigrant population, but they do not actually have above replacement rate amounts of kids, so they are going to require more immigrants to take care of them later on. Also, the children of immigrants have non-immigrant level fertility rates. So, it's not a long term, sustainable way to "replace the aging population."

On top of this, immigrants often want to bring their elderly relatives with them when they are possible. I know there are some ways to try to mitigate this (e.g., immigration limits, charging them extra fees on immigration), but at some point there becomes a large enough immigrant voting bloc that this changes. Now you have extra, unaccounted for elderly people that are required to be looked after.

I have no idea what the solutions are, but if we are trying to plug the gap through immigration, it'll require perpetual immigration. Most countries globally are now at below replacement fertility rates, so this opens up a huge can of worms. I'm sure I'm missing something obvious, but it doesn't seem like anything other than a quick band-aid or a solution that's doing anything other than adding "debt" to the issue.

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