Stephen Colbert's Late Show Ratings A Hit In Chicago

CHICAGO (CBS) -- Based on the overnight Nielsen ratings, Stephen Colbert is a big hit in Chicago--at least on opening night.

The Northwestern University and Second City alum, debuted as host on the "Late Show" on Tuesday, with George Clooney and Jeb Bush as his first guests.

In Chicago, his show ranked No. 1 its time period, and his household ratings (7.1/15 share) were a 238 percent increase over David Letterman's (2.1/5) year-ago average. Letterman stepped off the Ed Sullivan Theater stage for the last time in May

Those numbers mean that an average of 250,000 Chicago area homes tuned in during the broadcast.

In the key demographic used by advertisers--viewers between the ages of 25 to 54--Colbert outpaced Letterman by a whopping 440 percent.

Against his key late night competition, Colbert top NBC's Jimmy Fallon by 50 percent and ABC's Jimmy Kimmel by 170 percent in the 25-54 demo.

The Chicago market ranked No. 5 nationwide among 25 to 54 year olds.