The answer in part would appear simple. based on projections regarding life span over the past 100 years and known retirement age and increase of medical insurance over the same time and force the employer to pay 100% of the cost AT THE TIME of pay into a fund. The fund should NOT engage in ANY form of gaming (Stocks etc) and should invest 100% into US treasuries. Thus if a policeman is paid $1500 for a weeks work and the retirement contribution for this week is $2500 the municipality would IMMEDIATELY pay the worker and the $2500 into the retirement fund.
I am all but certain this is not what most municipalities intended…