Also very predictable exenditures over time, which increase with an aging population with decreased firtility rates. Which have little to do with actual firtility but are just a measure of kids vs parent ratio, it might play a role though. Everyone always forgets that it is entirely predictable but nobody does something about it because it hurts.

Also doesn't help if you borrow against the money put in. The US is not alone in taking money from the baby's/old peoples fund unfortunately, same happened here but worse the money was just taken. Although it was mostly spend on education and construction so there is that at least.