I agree that BTC is not, but I thought it was fairly well understood that social security was a mandatory Ponzi scheme.

From Wikipedia: "A Ponzi scheme is a fraudulent investment operation that pays returns to its investors from existing capital or new capital paid by new investors, rather than from profit earned by the individual or organization running the operation."

Social security does exactly that, and its recent failure predictions by the CBO are caused by the population failing to grow at rates that could sustain it. If more people aren't paying into it than those withdrawing from it, and it fails as a result, does that not match the definition of a Ponzi scheme?