Social Pyramid Scheme

How I learned to stop worrying and love the demographic time bomb by Nick Silver (IEA):

Most Western countries have some form of unfunded or pay-as-you-go (PAYG) pension system. These are effectively pyramid selling schemes, where one generation sells on its pensions commitments to a new generation.

Pyramid selling relies on being able to find a new generation of suckers, which is what the argument for more people proposes - new babies and immigrants being the next generation of suckers. This is no long-term answer - it's just building a bigger pyramid.