• by Wayne Friedman , May 28, 2010

Despite some lower ratings for its heavyweight show "American Idol," Fox gained overall in key viewers from a year ago -- winning another broadcast season, its sixth time in a row.

In the viewer group that advertisers focus on most -- 18-49 viewers -- Fox landed in first place again with a 3.7 average rating, 3% higher than a year ago.

Contributing heavily here was that Fox had a vastly improved fall quarterly period, winning that part of the season for the first time ever-- thanks to continued strong ratings from "House" and good viewership from newcomer "Glee." "American Idol" lost 9% this year in 18-49 viewers from a year ago.

CBS came next with a 3.2 rating, up 3%. This was mostly due to the airing of the Super Bowl, which always adds to the coffers of any network that runs the big event. Even then, CBS gained from improved ratings from "The Big Bang Theory," "NCIS" and newcomer reality effort "Undercover Boss." On the downside, "CSI" -- once its big Thursday night player -- dropped substantially, down 25% from the year before.

NBC had another rocky finish, but one big event saved the network from worse news.

While running "Jay Leno" at 10 p.m. hurt the network big-time versus its comparable ratings of the year before, the network's prime-time Vancouver Olympic coverage in February buffeted some of this with higher average viewership.

But there is still work to be done, as a number of established shows went south: "Law & Order: SVU" down 19% in 18-49 viewers and the original "Law & Order" sinking 25%. Both shows lost ground mostly from the fallout of moving out of their 10 p.m. time periods due to "Leno." Like "Law & Order," "Heroes" will not return next year. It lost 32% of its key viewership this season. At the end of the year, NBC finished at a 2.7 rating, down 4%.

All this left ABC at the bottom of the heap.

ABC suffered -- as other networks have -- from long-in-the-tooth shows losing steam. "Desperate Housewives" sank 17% year-to-year. On the positive side, ABC was able to launch a bunch of new comedies on Wednesday night, including the high-flying "Modern Family."

CW turned around a dismal 2008-2009 season to lift its key 18-34 numbers 10% to an average 1.1 rating in the 2009-2010 season. (Its 18-49 number stood at a 0.9 rating) "Vampire Diaries" was one of the main reasons, as well as some growth with "Gossip Girl." But one-too-many spinoffs from Fox's old prime-time lineup -- "Melrose Place," for example -- didn't click.

Among total viewers, there was generally better news: CBS was again the leader with 11.8 million, virtually unchanged with a 0.1% gain. Fox grabbed 2% more to reach 10 million, good for second place. ABC was in third place at 8.6 million -- off 4% -- and NBC rose 5% (again from the Olympics) to land at 8.2 million. CW improved 1% to 2.0 million.

But networks are getting older, with almost every programming demo climbing. The overall broadcast network median age is 50.9, up from 50 a year ago and higher than the 47 median age in 2005. Fox's median age is 44; NBC is next at 48. ABC's median age is 50, and CBS came in at 54. CW is at 33.