For detractors... Social Security in the US is one example. It literally depends on having a larger input base than the output. The expectation of GDP growth

For detractors... Social Security in the US is one example. It literally depends on having a larger input base than the output. The expectation of GDP growth is another, but without population growth, it's unlikely to be realized perpetually. I'm fine with that, but our over-leveraged financial system isn't.