After four weeks of the 2010-11 broadcast season, CBS's adults 18-49 ratings are now slightly below (-1.1%) where they were at this point last season, while the CW's and NBC's ratings are still slightly ahead of last season's.
And while ABC is 8.4% behind last season's ratings, the worst ratings slippage this Fall has come from Fox. Fox is down 12.2% vs. their adults 18-49 ratings last season and that's almost certain to get worse as they get hit by the bad year to year comparisons between the ALCS last year (with the Yankees) and the NLCS this year. No Yankees in the World Series, and short series would make things even worse.
Broadcast network season ratings overall: My calculation (not Nielsen's) of the average adults 18-49 ratings season to date for all 5 English broadcast networks is 4.3% below the season to date ratings average through week 4 of the 2009-10 season.
CBS maintains its season lead in primetime adults 18-49 ratings for the season after two weeks averaging a 3.3 rating. ABC, NBC and Fox are now tied in second place with a 2.8 adults 18-49 ratings average.
CBS remains well ahead in the press release friendly season to date average viewership.
Each rating point is a percentage of the US TV population in that demographic group and equals: a 1.0 adults 18-49 rating equals 1.315 million adults 18-49
The network's average viewership is charted in millions of viewers, just like we report all other average viewership information on the site, and adults 18-49 is charted as ratings points. Note the units (million viewers on the left, rating on the right) below the bars.
Note that these season average ratings are "Most Current" measurements which are Live+7 day DVR viewing when available (2+ weeks after airdate), combined with LIve+Same Day DVR viewing for the most recent 2 weeks.
Nielsen TV Ratings Data: ©2010 The Nielsen Company. All Rights Reserved.