Scripted TV series that attract older viewers mostly have one thing in common: Washington.

On each of the major broadcast networks last season, the scripted series with the oldest median age were set in the capital.

Median age is the point at which half the audience is younger and half is older, explains Magna Global USA, the ad-buying company that conducted the annual study of median viewer ages for broadcast series.

Oldest median age (OMA) is relevant in an industry that worships youth because it generally means the crew and cast should start looking for their next jobs.

And a Washington setting seems to be something of a buzz kill for younger viewers. People living there may look around at all the bright-eyed, bushy-tailed interns and think, "What a young people’s town Washington is!" but in the real world, where people mostly get their impressions of Washington from television, D.C. is old.

"Because old people are politicians," explained an exec at one network, and shows about politicians, he assured us, "are the least appealing ... to young people."

It’s true enough - many of these shows are about politics.

For instance, ABC’s scripted series with the oldest median age last season was Commander in Chief, starring Geena Davis as the running mate/publicity stunt turned POTUS. Median age: 55 years. Bye-bye.

NBC’s OMA scripted series? The West Wing tied with E-Ring. Set at: White House and Pentagon, respectively. Median age: 54. See ya.

But not all of these Washington-set series are about politics.

Fox’s Bones is about a young, beautiful forensic anthropologist who uses dry old bones to solve really old murder cases at some place called the Jeffersonian Institution in Washington, aided by totally hot FBI agent David Boreanaz.

And yet, median age: 44 - which in Fox years is like 100.

But if you really want to wow your friends, spring it on them that the Fox series packing the oldest median age, scripted or non-, is not Cops or America’s Most Wanted: America Fights Back or even The Simpsons, which just wrapped its 17th season, making it the oldest scripted series on broadcast TV.

It’s 24. The median age of the 24 audience is 45 years.

24 is about Washington. Yes, the president of the United States seems to spend a lot of time in Los Angeles, campaigning or just hanging out at his L.A. ranch.

But the government that Jack Bauer tries so hoarsely each gawdawful day to save is in Washington. And based on this series’ median age, you can take the TV POTUS out of Washington, but you can’t, in the minds of viewers, take the Washington out of a show about saving or assassinating POTUS.

Don’t take my word for it. Just ask the show’s ardent fans, who, as we learned during the Heritage Foundation’s 24 forum in Washington last week, include Supreme Court Justice Clarence Thomas, radio talker Rush Limbaugh, Vice President Dick Cheney, Defense Secretary Donald Rumsfeld, President Bush the Elder and Department of Homeland Security Secretary Michael Chertoff.

CBS’s OMA scripted show is NCIS - 56 years - set at the Naval Criminal Investigative Service at the Navy Yard in Washington. NCIS is also not canceled. But CBS is an older-skewing network - median age overall in prime time is 52 - so 56 doesn’t look so bad there.

NCIS is actually tied with CBS’s Cold Case in terms of median age; Cold Case is set in Philly, not Washington.

But, it can be argued, that the Cold Case median age is more about the fact that it snags viewers from its lead-in, 60 Minutes, which has the oldest audience on broadcast TV. Its median age last season was 59.