I don't really know which countries have private pension funds.

Certainly in countries with an ageing population it's difficult to fund retirement pensions with tax revenue.

Supposedly the USA is one of the few places where you get paid back what you paid in plus interest earned, whereas here in Estonia for example we pay for the current retired people and once we're retired, IFF the system still functions, younger people will pay for our retirement.

Pretty much a ponzi scheme that I don't expect to still be functioning by the time I'm old, we're an aging society and there's going to be fewer taxpayers in the future.