Here are some of the Chicago numbers i don't know how updated or acurate this info is but gives you an idea of staffing levels
CHICAGO ARTCC
Illinois
Type of Facility: Air Route Traffic Control Center
Serves northern Illinois, eastern Iowa, southern Wisconsin, northern Indiana, southwestern Michigan
Authorized certified controllers & trainees: 460
Number of certified controllers, actual: 398
Number of trainees, actual: 42
Percent staffed: 96
Number of certified controllers
eligible for retirement at end of fiscal 2007: 91
CHICAGO TRACON
Illinois
Type of Facility: Terminal Radar Approach Control
Serves Aurora, Chicago Midway, Chicago O'Hare, and Palwaukee airports
Authorized certified controllers & trainees: 101
Number of certified controllers, actual: 75
Number of trainees, actual: 17
Percent staffed: 91
Number of certified controllers
eligible for retirement at end of fiscal 2007: 36
CHICAGO O'HARE INTL ATCT
Chicago, Illinois
Type of Facility: Air Traffic Control Tower
Authorized certified controllers & trainees: 71
Number of certified controllers, actual: 47
Number of trainees, actual: 11
Percent staffed: 82
Number of certified controllers
eligible for retirement at end of fiscal 2007: 11
CHICAGO MIDWAY ATCT
Chicago, Illinois
Type of Facility: Air Traffic Control Tower
Authorized certified controllers & trainees: 28
Number of certified controllers, actual: 25
Number of trainees, actual: 3
Percent staffed: 100
Number of certified controllers
eligible for retirement at end of fiscal 2007: 8
http://data.gannettnewsservice.com/airtraffic/airindex1.php