Byline: JOAN ENGEBRETSON

Trendsetting Generation X types used to be all over. Clad in flannel shirts or bound for Lollapalooza, we saw them everywhere from Seattle grunge-rock haunts to Paris runways to the cover of Newsweek. Today, this generation - born between 1965 and 1976 - is forming families and entering its peak-earning years. But when it comes to television, Gen X is practically off the radar. With a few notable exceptions, such as Trading Spaces and Sex and the City, today's thirtysomethings rank as TV's accidental demo for programmers and a virtual black hole for advertisers trying to reach them with marketing messages. Fear has set in.

"The median age of network television viewers is well above even the top end of the 25- to 39-year-old age group, and it's not much better with cable," says Jon Mandel, president of media buying agency Mediacom.

Another raft of network and cable TV series came down pilot pipeline this spring, and Hollywood and Madison Avenue's bets appeared again to be oddly placed. The age group that has forever powered consumer spending - the young adult in his or her prime family-, household-formation and peak-earning years - was missing in action amid focus on the two flanking generations, Boomers and Generation Y. One can understand the TV industry's hesitance to risk alienating the juggernaut Boomer group that has been the goose that laid the golden egg for the better part of three decades. What's more, Gen Y represents an about-to-be mega-sized population that's expected to reinvigorate the economy for decades to come.

But, where does that leave X, marketing and media segmentation's perennial second-class citizenry? More important, if the smaller population cohort of Xers and their earnings, family and household formation behaviors are expected to galvanize spending along the lines that Boomers did during their late 20s into and through their 30s, then where will TV fit in as a spending catalyst? In November 1990, when the 18-to-35 age cohort was dominated by Boomers the average prime-time network show received a 6.8 rating, according to Nielsen Media Research. As of November 2003, when Generation X dominated the same age group, the average prime-time network show received a rating of only 2.4.