The audience that tuned in for Katie Couric's first week on the "CBS Evening News" shrunk by Friday, when the broadcast averaged 7.4 million viewers, 45 percent fewer than watched her Sept. 5 debut, according to Nielsen Media Research.

Nevertheless, CBS remained in first place for the holiday week, averaging nearly 10.2 million viewers between Tuesday and Friday and garnering the perennially third-place newscast its first weekly ratings win in more than five years.

The "NBC Nightly News," usually the top-rated broadcast, came in second with an average of more than 7.1 million viewers for the week, excluding Thursday, when the network broadcast a National Football League game. ABC's "World News" followed in third, drawing an average of nearly 6.9 million viewers for the week.