The issue here is to dedicate x% of GDP to supporting retired people (and other entitlements) and whether that is possible/sustainable. A reasonable value of x% is always possible and, by definition, sustainable for any reasonable choice of x.

One way to do this is for that to be a sovereign outlay and to collect y% GDP in taxes to fund that, and other government programmes.

People think they can pay z% in taxes, and save (y-z)% into a private investment scheme.

But the fact is that money is not a thing and sovereign outlays are not in a zero-sum game with taxes and savings.

However, the illusion that money is a thing seems to be psychologically necessary in order for a fiat money system to work. Because, if people think that fiat money is not a real thing they will think it's worthless and destroy the fiat part of the fiat money system.

By laying out pros and cons we risk inducing people to join the debate, and losing control of a process that only we fully understand. - Alan Greenspan