The youth movement in broadcast network programming would seem to contradict a major demographic shift: the aging of America.

But agency media executives say older audiences are easier to reach than programming trends would suggest-especially as the first baby boomers turn 50 next year.

"It's not difficult to find older viewers," says Jack Irving, exec VP-media director, Saatchi & Saatchi Advertising, New York.

Mr. Irving's list of 1994-95 prime-time network TV vehicles for reaching viewers age 50 and up includes time-tested shows like "Murder, She Wrote" and "60 Minutes." However, his list for reaching viewers 35 and up includes current hits "E.R.," "Home Improvement" and "Seinfeld."

"Older viewers will watch younger shows," says Mary Ann Foxley, VP-media director at Leo Burnett USA, Chicago. "But there's no amount of convincing that will get a 21-year old to watch 'Murder She Wrote.'"

Americans age 55 and older view more television than any other demographic break, according to Nielsen Media Research. With the number of Americans age 50 and up projected to increase more than 60% by 2020, that means more people will be camped in front of TV sets.

In addition, agency media buyers say older viewers are more loyal to network TV and less likely to subscribe to cable.

Nonetheless, by shifting "younger," there's a good chance the networks may reach viewers 18-plus while retaining older viewers. That's particularly true for aging baby boomers who are young at heart and have demonstrated that they're the least likely to change their viewing habits.

"Many baby boomers adhere to the Peter Pan principle: they won't grow up, they listen to rock and roll, and they still watch sitcoms," says Jim Bell, president of Media Connections, the media arm of Grey Advertising, New York.

Two main factors are driving this search for youth:

Advertiser demand, especially with new network TV dollars coming from youth-oriented products such as computers and videogames.

The success of Fox, with high-cachet shows like "Melrose Place" and "The X-Files."

In response, the Big 3 have slotted young-adult oriented programming such as the upcoming programs "The Drew Carey Show" on ABC and NBC's "The Single Guy" and "Caroline in the City."

By devising programs that appeal to a young adults, there's a good chance their parents will join in-at least, that's what the networks hope.

"The networks aren't trying to alienate older viewers, but they are intent on reaching the core market, the attractive 25-to-49 age group," says George Hayes, senior VP-director of agency of record accounts, McCann-Erickson Worldwide, New York.

"What the networks seem to be doing is realizing .*.*. that they can't have a schedule in which all shows on a given night will chase one audience.... but to have more of a mix," says Steve Grubbs, senior VP-director of national TV buying at BBDO Worldwide, New York.

He adds that the early morning and news dayparts especially are the "hot" dayparts in which to reach the 35-plus audience.

The networks, too, are quick to defend their youthful orientation as providing programming that's more inclusive rather than exclusive. Something for everyone is the goal, network executives say.

"Clearly, we've oversold the perception of a youthful appeal, but the reality is we're going to have a very balanced programming schedule," states George Schweitzer, CBS exec VP-marketing.

"We're not going to be Fox, or MTV or even ABC or ESPN, looking only for the 18-to-49 male," the executive adds. "We have set up as a goal to lower the middle age group to a younger audience, to improve our demographic reach, but we're going to do it based on the strengths of CBS."

To hopefully achieve this balance, CBS' 11 new series for this fall includes younger-skewing comedies like "Dweebs," about people plugged into the Internet, and "Can't Hurry Love," about the dating experiences of Manhattanites.

It also features shows like "Central Park West," a soap opera about glamorous, ruthless New Yorkers starring Mariel Hemingway and Lauren Hutton, aimed at the 25-54 demographic.

Media executives agree the networks really don't have much to lose by pursuing youth. Ratings this season were generally down, perhaps indicating viewers have tired of current offerings, and an infusion of new programming may well revive viewing in all demographic groups.