After twelve weeks of the 2012-2013 broadcast television season (through Sunday, December 16, 2012), NBC is in first place among adults 18-49, with a 3.1 rating average, up 24% from last season. CBS was second, with a 2.9 rating average, down 12% from the prior season. ABC was third with a 2.5, down 4% from the previous season FOX was fourth with a 2.4, down 27% from last season. The CW finished last with a 0.8 adults 18-49 rating average, down 11% from the previous season. Note that the CW season/season comparison is an apples/oranges one because they began their show premieres late and aired a week+ of repeats and summer shows at the start of the 2012-13 season.
Among total viewers, CBS is ahead for the season averaging 11.827 million viewers. NBC is second with 8.825m, followed by ABC with 8.739 m, FOX with 6.737m, and CW with 1.9 million.
Each adults 18-49 rating point is a percentage of the adults 18-49 US TV population and equals 1.265 million adults 18-49. The season-to-date numbers are "Most Current" ratings, which are Live+7 Day for all but the two most recent weeks and Live+ Same Day for the two most recent weeks.
You can see last week's broadcast network primetime weekly TV ratings results here.
Nielsen TV Ratings Data: ©2012 The Nielsen Company. All Rights Reserved.