[alkonaut]

We need to separate the concept of pensions from the concept of retirement. If retirement should go away as a concept, that would mean it is somehow impossible to put away any money so that you don't need to work your last years. Obviously unless something radically happens to the way the global economy works, many people will be able to set aside 20% their pay, and and live the last 20% of their lives on that.

But pensions on the other hand usually involve some sort of government system which often ends up trapped by demographic swings. The key for a pension system is this: don't allow it to depend on demographics. Make sure each generation provides for it's own pensions.

[bluGill]

Fundamentally you cannot make each generation provide for itself. Most food cannot be stored for 20 years, so we need to have current day farmers. Even if you say automation, we still need someone to maintain those machines when they break. That means if you retire it must be on some store of value that the future generations want and will trade for food.

I used food above, but lots of other things likewise need current work. You cannot retire and sit on a log watching birds, you need to get lots of things from society.

[alkonaut]

Yes of course a society in demographic collapse will fundamentally not work. I'm talking about providing for your own generation financially here. Society must manage the task of supplying enough hands to do the work, which could mean e.g. maintaining a reasonably stable fertility rate of at least 1.8 over time for example (Or a corresponding immigration to ensure the same thing). Otherwise yes of course eventually you have a country that is a retirement home with no staff...

[livrem]

Lower population works if we can build better machines. In the best case it can work even for a retirement home country. It requires some political improvements to make sure the machines are employed in a way to make that possible of course.

[alkonaut]

So long as the demographics shifts are gentle enough it's also not a huge problem to have an aging or shrinking population. Higher efficiency will help maintain standard of living with an aging or shrinking population though. The only think important to not have an "end of retirement as we know it" is to not have wars, hyperinflatoin, or a complete demographic collapse (e.g. extremely low fertility rates for a generation).

[trashtester]

You could always pay for retirement by building a few houses out of Roman concrete, that would stand for 1000 years with no maintainance.

[bluGill]

That doesn't pay for the feed you need to retire on.

[trashtester]

Sure, but if the current generation would build housing with very low maintenance costs, at least that would diminish the load on the next generation by noticeable amount.

Just storing value as cash just means that you have a greater claim to the productivity of a given society than other people, it doesn't necessarily "grow the pie".