• by David Goetzl  @dgoetzl, June 27, 2007

The Big 4 are all over the big 40. With Fox's median age increasing to 42 this season, all the major broadcasters, for the first time, have a median age north of 40, according to a new report from Magna Global.

The age increase from 39 a season ago to 42 comes as Fox saw ratings drop by more than 10% in the 18-to-34 demo, a segment that accounts for 23% of its average audience.

ABC saw its median age increase from 46 to 48 this season, while NBC--perhaps helped by 18-to-34 hit "Heroes"--remained flat at 49.

It's possible that next season, ABC and NBC could both have about half their average audience above the 18-to-49 demo, which they claim as their sweet spot. CBS saw a slight increase this season from 52 to 53.

Network television's aging process includes the median-age average for the Big 4 increasing from 46.5 to 48 this season--with each network experiencing significant declines in the 18-to-34 demo. Also for the first time, the average combined median age for ABC, NBC and CBS reached 50, reported Magna Global.

Another first--none of the broadcast late-night shows had median ages below 40, including Fox's "MadTV," the youngest-skewing entry, and NBC's "Saturday Night Live," at 45 up from 39 five seasons ago.

Still, higher median ages are hardly a slam. The just-wrapped broadcast upfront market proved surprisingly healthy. And a network can do well, yet experience a median-age increase, if a couple of hits skew older.

ABC's increase, according to Magna Global, is due in part to an older audience for "Dancing with the Stars." It airs twice a week and is considered a huge hit.

Despite its median-age increase, Fox is still viewed by many advertisers as a must-buy to reach younger viewers. It dwarfs the CW (with a median age of 32) in the CW's target 18-to-34 demo by an average of 1.4 million, but has four solid shows in the 18-to-34 demo: "American Idol," "House," "Family Guy" and "The Simpsons."

But the huge hit "Idol" is contributing to the median age increase, with its attraction for an older audience and family-viewing appeal. (It's the No. 1 show in the 25-to-54 demo by a long shot.) Over the five seasons "Idol" has been part of the network's regular schedule, Fox's median age has risen strikingly by 20%, from 35 in 2002-03 to 42 this season, according to the report. Over the same period, its percent of audience over 40 increased from 41% to 53%.