I'm surprised that WBBM is so far ahead of WGN. I believe the Score is in the $12 Million range.

The following are the Top 10 billing Chicago radio stations for 2011, a Chicagoland Radio & Media exclusive:
1. WBBM-AM/WCFS-FM (News/Sports) $48,000,000 -- CBS Radio
2. WTMX-FM (Hot AC) $36,000,000 -- Hubbard Broadcasting
3. WGN-AM (News/Talk/Sports) $35,500,000 -- Tribune Broadcasting
4. WOJO-FM (Mexican Regional) $24,000,000 -- Univision Radio
5. WUSN-FM (Country CHR) $22,000,000 -- CBS Radio
6. WVAZ-FM (Urban AC) $20,500,000 -- Clear Channel Communications
7. WGCI-FM (Urban) $18,700.000 -- Clear Channel Communications
8. WBBM-FM (CHR) $18,000,000 -- CBS Radio
9. WDRV-FM/WWDV-FM (Classic Rock) $16,100,000 -- Hubbard Broadcasting
10. WKSC-FM (CHR) $15,900,000 -- Clear Channel Communications

Looking at the bigger national picture, here are the Top 10 billing U.S. radio stations for 2011:
1. WTOP-FM (News) $64,000,000 -- Hubbard Radio - Washington, DC
2. KIIS-FM (CHR) $57,000,000 -- Clear Channel Communications - Los Angeles, CA
3. KFI-AM (News/Talk) $48,100,000 -- Clear Channel Communications - Los Angeles, CA
4. WBBM-AM (News) $48,000,000 -- CBS Radio - Chicago, IL
5. WCBS-AM (News) $47,500,000 -- CBS Radio - New York, NY
6. WHTZ-FM (CHR) $46,000,000 -- Clear Channel Communications - New York, NY
7. KROQ-FM (Alternative) $42,000,000 -- CBS Radio - Los Angeles, CA
8. WINS-AM (News) $42,000,000 -- CBS Radio - New York, NY
9. WLTW-FM (AC) $42,000,000 -- Clear Channel Communications - New York, NY
10. WFAN-AM (Sports/Talk) $40,500,000 -- CBS Radio - New York, NY