WASHINGTON - Scripted TV series that attract older viewers mostly have one thing in common.

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 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 here 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. 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 and former vampire 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 in this whimsical drama series, campaigning or just hanging out at his L.A. ranch place.

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 more ardent fans who, as we learned during the Heritage Foundation’s ”24” forum in Washington just 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.

For comparison’s sake, the median age of the audience on Fox’s animated “American Dad” is 27.

And the median age for “The Simpsons” is just 29 - exactly the same as its median age during the 2001-02 TV season. The 16-season-old “Law & Order” on NBC has a median age of 52.

Which, brings us to an interesting point about median age and animation.

While audiences for scripted shows featuring actual people on the screen tend to age, at varying rates (over the past two seasons, the median age for NBC’s “Las Vegas” shot up six years and for “Will & Grace” five years), series starring toons can remain forever young.

That’s because Bugs Bunny never ages and Bart Simpson still looks like a juvenile delinquent 17 years later. Their stars frozen in time, these shows have an easier time recruiting new, younger viewers, while their original aging fans tend to grow out of the shows (or their wives won’t let them watch anymore) - a win-win for a network trying to keep down a show’s median age.

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, like we’re doing here, 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.