This is just one component of the US Federal Government's hundreds of trillions of dollars in unfunded liabilities. "Gradually then suddenly" comes to mind.
Government employees generally have sweeter pension plans compared to private-sector employees, but government pensions are purposely underfunded. No worries for government employees: taxpayers will pick up the slack.
The maths behind defined benefit pensions just doesnt work... They're great for the employee though, just terrible for employers. They are another example of the fiat magic money tree. ... Say you are lucky enough to be working for the NHS in the UK. ... You earn ave £30k and work for 30 years. Yearly pension contributions are about 25%; 10% employee and 15% employer. So, it's very expensive! ... After 30 yrs, total payments in are £225,000. You get about £16,600 pa. when you retire after 30 yrs (30x(1/57 salary for each yr service, each scheme has its own multiplier). Which uses up your £225k after about 14 years (ignoring inflation), BUT... Average life expectancy at 65 is 20 yrs, so you outlive your pension pot by 6 yrs. Plus your pension is actually index linked, so it goes up every year. So the pension fund has to find the difference! In reality, yes some schemes may invest to grow the pension pot (the nhs does not) but that introduces capital risk, so hey ho that cuts both ways, however the scheme takes the risk, not the employee, which is why they are great pension schemes if you have one... And btw, the UK already has an £8billion pa public pensions deficit, yes, funded by the taxpayer.