>The UK system takes the national insurance contributions of workers but doesn’t invest them in anything on behalf of the individual. So despite decades of payments you technically have nothing at the end and survive on the goodwill of the government and current taxpayers. That works right now because of the population pyramid.

That's how Social Security works in the United States as well.

I believe it’s tied to your earnings in the US though, which it isn’t in the UK.

I also have a number of qualifying years in the UK when I didn’t work, and for decades you could buy a year contribution for about £150. The payout is £12,500 per year.