In the three decade decline trend for broadcast TV primetime ratings there are seasons that are a bit better than the trend (like last season), and some seasons that are worse than the trend.
After two weeks of the 2012-13 season, it's shaping up to be a lot worse.
In first two weeks of the 2011-12 season, in the advertiser important adults 18-49 Live+Same Day DVR ratings, this season ABC was down 21% in week 1 and 10% in week 2, CBS was down 27% in week 1, and 17% in week 2, Fox was down 24% in week 1 and 19% in week 2. Mostly by virtue of its move of The Voice to the Fall, NBC is the only network to rise, it's up 12% in both week 1 and 2 vs. last season. No valid comparison yet for the CW, unlike recent seasons when they started their shows "early", this season they are starting "late".
The broadcast networks know this season's drop from last season isn't pretty, and their PR operations will be putting out a blizzard of Live+this and Live+that DVR ratings to distract attention from it, but you can look past that to the reality.
While the C+3 Day commercial ratings are all that *really* matter to the business of the broadcast networks, their trends are likely highly correlated with the trend of the Live+Same Day program ratings, and I'd be startled if they showed trends that were much different than the Live+Same Day program ratings.
However, if any network PR department would like to provide me with your season to season C+3 day commercial ratings trends and prove me wrong, I await your emails!