A major problem is that this is a case of I'll be gone, you'll be gone.
The union leaders and the politicians - typically in their 50 to 70s - who made the promises will be dead by the time the 25 year old new hires try to collect their pensions at 55 or 65. The incentives are all sorts of screwed up and it's very difficult to create a healthy set of constraints for this kind of bargaining.
> ... create a healthy set of constraints for this kind of bargaining.
They should simply put the burden of new obligations (debt or pension guarantees) on individuals rather than on the city. If you live in a municipality when they take on a bond for a stadium, or agree to pension payments, then you pay those debts regardless of where you have moved to. Or put the obligations on property, so people have an interest in not burdening themselves or their investments.
The union leaders and the politicians - typically in their 50 to 70s - who made the promises will be dead by the time the 25 year old new hires try to collect their pensions at 55 or 65. The incentives are all sorts of screwed up and it's very difficult to create a healthy set of constraints for this kind of bargaining.