Ponzi schemes, by definition, collapse at the end: each stage of "investors" have to be exponentially larger than the previous, and there's only so many people

Ponzi schemes, by definition, collapse at the end: each stage of "investors" have to be exponentially larger than the previous, and there's only so many people that can be involved before it becomes impossible to reproduce the next stage. The majority of participants get nothing, for that reason. State pensions don't work like this. Even in disadvantageous demographic situations, the majority of people get something comparable to what they put in. Even in the most aged populations you don't go from X to 0; you go from X to (1 - c)X, where c is relatively small; that is, much closer to 0 than to 1.