>

I especially worry for the growing number of childless people who will have no family to fall back on when shit hits the fan on elder care. 
Healthcare already employs such a large percentage of our population. Even if working conditions improve, I just don’t believe we have the capacity to allocate sufficient numbers of workers to care for a population with the amount of healthcare demands we have and expect to have in the future.
Population decline by itself isn't a bad thing. The rate of population decline is what is worrying. 
I live in a country that had just under 4.8 million people 30 years ago. According to last year census, we are just above 3,8 million now. By the end of this century we will be perhaps below 2 million. Whatever your political views, the idea that that sort of population decline wont have negative effects on the country and society is completely delusional.
And we are not an exception. Developed countries around the planet are going to have rapid population decline in coming decades.

Innovation comes from a well educated population. Not from a large population. 

If you live on a planet that has a bunch of old people, instead of young people, that means that a greater proportion of money and resources that would have otherwise been spent on education or innovations now has to go towards medical care for the old. Which means less innovation. 
Also. All other things being equal, would a planet with a million people or 10 billion people have more innovation ? The answer is obviously 10 billion. Larger well educated population will have more innovation than a smaller well educated population. Didn't think that was controversial. >


All other things being equal, would a planet with a million people or 10 billion people have more innovation ? The answer is obviously 10 billion. Larger well educated population will have more innovation than a smaller well educated population. Didn't think that was controversial.

The controversial part is where you need to gamble on those 10 billion people always being able to find technology that will save the day. Because if they don't, we are doomed.
On the other hand, if the planet only had 1 million, carbon emissions would be drastically reduced beyond our wildest dreams, and there would be plenty of resources for all. >



On the other hand, if the planet only had 1 million, carbon emissions would be drastically reduced beyond our wildest dreams, and there would be plenty of resources for all.


As someone worried about carbon emissions, do you know what percentage of the atmosphere is carbon?  And what percentage is the ideal? >

It's not that there's a particular number that's ideal, and the problem is that we've stayed from that number. It's that it's changing so rapidly that it's snowballing faster than life in general, and human society specifically, can adapt on a large scale. If the global average temperature rose by 5°C over the next millennium, it probably wouldn't be too big a deal. But half that over the next 100 years is a very big deal.
I guess if i had to give you a direct answer, it would be approximately the amount that we've spent the last few millennia learning to live in. Decisions from that are fine as long as they happen slowly enough that we can adapt socially, and other species can adapt genetically, to the change. >

The atmosphere is currently 0.04% carbon.
Are you saying that 0.05% too much and 0.03% the ideal? Or is 0.04% the ideal?  What happens if it doubles and reaches 0.08%? Catastrophe? >

You're really glossing over the whole "lots of old people, very few young people" problem. >

Yeah, OP says “people should be saving money for retirement, so lots of old people being retired shouldn’t be a problem”
This is a fundamental misunderstanding of how the world and the economy works. It doesn’t matter how much money people have saved for retirement if there aren’t enough working people to make the stuff they need to buy with that money.
It isn’t like saving for retirement means you are saving cans of food to eat later, like you are a squirrel burying nuts for the winter. You are saving money that you hope to trade in the future to someone else for your food and basic needs. This will only work if there is someone to trade your money to; if society is full of old people who have saved up money for retirement and not very many young people to make the food and things, then you are just going to get rapid inflation as all these old retired people try to trade that money to a dwindling number of productive people.
If this is hard to understand, just imagine the extreme… what if ALL the people are old, and they have all saved a ton of money…. Who are they going to pay that money to? No one is making food, they are all sitting on their pile of money wanting to buy food. The money would be worthless. >

ALL the people won’t be, so such an extreme is absurd. reductio ad absurdum >

I wasn't claiming the extreme example would ever happen, I was trying to show why having fewer working age people would lead to problems by using a hypothetical case of having no working age people... sometimes it helps to see an abstract thing like that by imagining the extremes.
Also, that isn't what reductio ad absurdum means; it is a form of argument where you show that if your argument wasn't true, you would end up in an absurd situation. >

Your argument isn’t true, and you end up in a state of absurdity. >

That doesn’t follow at all. I was not arguing that we are in a world, or even headed to a world, where there are no working age people. That wasn’t my argument.
And even if my argument WAS absurd, it still isn’t a reductio ad absurdum. It isn’t something you say to counter an absurd argument. It is a logical argument where you point out that your own argument has to be the case or you reach a contradiction >

My argument is that not all people can ever all be old. If that isn’t true, we end up in your absurd situation. reductio ad absurdum >

you are still using RAA incorrectly, you have the implications mixed up. >

Well, how ‘bout we admit your premise (all old people) is absurd and entirely unhelpful in advancing any argument. >

no. I'm not even the person you originally started to object to, but their argument is clear.
The premise is "in an aging population, there will be demand for goods and services that outstrip our ability to supply it, which will result in inflation", with the (perhaps implicit) conclusion that "world population decline is a major problem."
They have used an extreme example for illustrative purposes in order to argue why the (far milder) premise holds, but that extreme example is not their actual premise.
If you want to refute their premise you need to engage with it as stated, explain why having only, say, 20-30% of the population (vs. current 50%)  in the working age bracket (25-65) would not lead to demand for goods/services outpacing supply and leading to inflation. >


Population really is the driver of power and economies. 

Say you want to open a business. Do you want to open it in a market with 300,000 customers or 300,000,000 customers? 
As a country, you want to have the largest population possible. If you lose too much population you lose your economic power. 
At a global scale, yes, a lot of innovation is driven by an educated populace, but it also stems from the unbelievably gigantic global market that creates demand for your products. 
Smartphones would not be as good as they are if it wouldn’t be a market of literally billions of customers. not to mention all the niche markets that would simply not be worth any investment into if there wasn’t enough of an international market for it. (the internet has enabled many of those markets in the first place by aggregating globally spread out customers into one neat virtual place.)

Age structure is hugely important. 

The last thing you want is a large amount of elders with only few people to run the economy. Unless you want 80 year olds to be working office jobs, You do not want 2 retired people for every working person. 
First, while people live longer, I would not consider a 70 year old today much more better capable of work than a 70 year old 50 years ago. It’s just that there’s a lot more of them now surviving until that age. 
Also while yes, people should be saving, most people don’t save as cash or investments. They choose to pay into pensions a set amount of money during their lifes and then get paid back later. That money isn’t saved by those institutions. It’s immediately payed out to the current retired, and when you retire, the youngsters’ money will come to you. If the ratio is too extreme, the working generation will have to burden the pensions. 
Gradual decline isn’t as bad, but for many developed countries, the decline is concerningly rapid. >

You don't understand the problem posed by an aging, shrinking population. 
Lets start with these three, because they're the same problem.

People are living longer healthier lives and are (or should be) saving to finance their retirement.
Ah! The poorly designed entitlement programs that just assumed indefinite population growth (see ponzi scheme). 
Deflation caused by an aging population.

LIFE ITSELF is a Ponzi scheme. We've always depended on younger adults to both take care of children, and take care of their elders, because they can't really take care of themselves. These 'entitlements' are simply how we do it these days, instead of shoving four generations into a single household and taking care of them that way. Which, if we still did, would have the same exact problem. More elderly, fewer children. Lots of folks just not having kids. The strain of taking care of the elderly will only get worse and worse as there's more and more of them, relative to the young. 
So unless you've got a solution to the 'retirees consume resource but don't produce resources' problem, you're going to need a healthy workforce to actually support them. It doesn't matter how much money they have if very little is being produced, transported, or maintained, because that money can't buy what doesn't exist. 
And remember, money is just a store of value, not something of actual value itself. You can't eat a fist full of dollars because it's not food. It won't heat your home because it's not gas or electricity. You can't call someone with it, because it's not a phone. You can't browse the internet with it because it's not a computer or internet connection. It's just some paper, if not just a number on a server somewhere. All it is is a bit of a social lubricant to make trade much simpler. This is why we can just print more of it (which is fine, within limits). Think of money as oil in an engine. The engine will seize up without it, but if your engine blows itself up, adding more oil to it won't make help any, just make the fire worse. 
The aging population problem really boils down to this. The elderly don't maintain infrastructure. The elderly don't pick crops in the field. The elderly don't operate power plants. The elderly don't manufacture. The elderly don't transport goods across the world. The more elderly you have, the larger percentage of your population you're dumping into the very basic maintanence of civilization. When this problem gets bad enough, everywhere begins looking like Flint, Michigan: You'll have water systems that needs maybe three or four times the maintenance to keep operating than you can actually throw at it. And this is across all sectors of civilization. 
At the end of the day, you can stuff money under your mattress. You can get into canning and/or jarring food and store a lifetimes supply of food in your basement. But you can't store a lifetime's worth of medical care, or internet access, or electricity. And we literally don't have enough water for everyone to remove a lifetime's supply from the water cycle. We NEED the infrastructure we have. Automation will only take us so far. It can make individual workers more productive in certain tasks, but we're pretty damn far away from the sort of post-scarcity fully automatic luxury gay space communism that it would take to actually run this hypothetical society. 

A decline in military strength.
Oh God. I'm not even going to touch this one.

You should. It's extremely important. You know why Russia went to war with Ukraine? Because Russian demographics are fucked. They will never be stronger. It's now or never. And now China is in the same exact boat. Modernizing will let them keep getting more powerful for several years, but they're going to peak. And when they do, they're going to start a war. They'll have no choice, unless they give up their ambitions. Something I REALLY don't expect the CCP to do. And you're going to see this happening with more and more countries, as they get more and more desperate and feel like their back is against the wall. Every regional conflict will flare up as national leaders realize that they can try now and maybe win, or not try now and definitely lose. 

Innovation comes from a well educated population. Not from a large population. 

Education helps, a lot, but it's also a numbers game. The more people you have, the more resources you have (human and otherwise) to throw at problems. It doesn't matter how educated you are, you aren't about to innovate a fusion powerplant in your basement with a box of scraps. >

Life itself isn’t a Ponzi Scheme. A Ponzi scheme is a term that has to stay more specified or there’s no damn point to using it. The critical idea of a Ponzi Scheme is that new investors are brought in to pay off old investors and that no products actually change hands, and no services are done. This qualifies social security but disqualifies life itself, as services and goods exchange hands.
For what it’s worth I disagree with OP on basically everything else, but he’s absolutely right to call out these poorly structured government welfare programs that were designed to fail. >


Unfortunately, because elders don’t have enough money to pay for adequate care, they will never get those caregivers. Workers will stay in better paying industries. We are looking at a potential for a crisis of elders dying of neglect.

The really sad thing is that it will be of their own doing. This is what happens when Boomers hoard wealth, vote for politicians that influence shit policies, help securitize healthcare, help undermine labor power and force people into other sectors of the economy to make a living. 
My friend works as a hospital administrator in a rural part of the state and they will not be able to care for the aging population. They can't find enough doctors and nurses. Not enough people are pursuing an education to become doctors and nurses are fleeing the field from burnout, being underpaid and COVID. 
Until the US makes major changes to benefit workers, strengthen labor rights, make education cheaper and more affordable for those scared away by sticker shock and the financial burden of schooling, our healthcare system will be a broken mess that can't support an aging population. A massive die-off of older, uncared for seniors will likely be inevitable.