A system by which the government guarantees all employed persons in the entire nation will get a certain percentage of their income by the time they retire.

This system has been fairly functional up until recently, with current demographic shifts making most current models unsustainable unless states increase the age at which a person may collect their pension.

This has effectively made most of these systems into a literal political time-bomb in the countries in which they have been implemented because the taxes that must be levied against individuals and the companies that employ them to pay for such funds has made it so that only the ultra wealthy or very well off can feasibly keep a private retirement fund, meaning that with every year the government increases the retirement age they are effectively forcing most of the population to work longer than they want to/are able to, which is shockingly very unpopular with voters.
Wealthy CEO: Oh boy I’m sure looking to retire at age 50 and leave my company to my son/daughter so they may do the same exact thing.

Average Employed Person: Damn it’s going to suck ass working until I’m 70 only to retire and have the National Pension Fund recipient age raised to 71
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