Please consider Chicago's Fiscal Stress: New Term, Same Problems.

Pension Payments Are A Growing Portion of the Budget

Years of poor funding exacerbated Chicago's pension obligations so that it may be infeasible to keep them solvent without modifying benefits. Chicago's four pension plans have a combined $20.1 billion unfunded liability and funded ratios ranging from just 24% to 57%.
 

image: http://4.bp.blogspot.com/-dI7BcyEkiTA/VUcYaVlVyqI/AAAAAAAAdnY/yAtifs7Igt4/s400/Nuveen1.png

click on any chart for sharper image

A Pension Payment Spike Looms in 2016