''These younger folks may not be big-ticket purchasers now,'' says a Ford spokesperson, ''but they may one day be. Ford wants to form a relationship with these younger buyers now and grow them up into our various brands.'' As for Honda, it has, according to a company representative, ''pretty much one of the youngest buying demographics of any car company out there. The Civic in particular — almost all the ads on the WB are for Civics. And we're on MTV all the time.''

And how many of these youth-oriented Civics, sticker-priced at a minimum of $14,000, are actually sold to people under the age of 26? One in five. Not so different from the 60's.

They'll catch on eventually. But advertising is a vast mechanism, risk-averse and inertia-driven, and like most multibillion-dollar industries it changes course with all the agility of an oil tanker. And so, for now, the polestar of the target demographic endures. It has gone from an ecstatic confluence of societal change and economic opportunity to a fusty business institution.

Of course, it's more than that as well. No matter how many dollars might be squandered in the process, you see in modern TV advertising what you see in, say, Greek statuary: a cultural key, a worldview whose increasing irrelevance to cold economic models only testifies to how compelling it remains for us.

In the meantime, the Fox network, eager to reassure advertisers made restless by its drop last year to second place among 18-to-34-year-olds, has just announced that this fall it will become ''bold, younger, more noisy.'' The network's new motto? ''It's Good to Be Bad.''