BYE, BYE, traditional American pie. For years we've been slicing the citizenry of this great land into Harry Homeowners, young marrieds, swinging singles, blue and white collars, haves, have-nots, teens, Bohemians, Mr. and Mrs. Front Porch U.S.A., blue-haired old ladies, mobs and snobs, Irving Upscale, Larry Lunchpail . . . bye, bye.

Jonathan Robbin stopped waving a long time ago. Robbin is the president of the Claritas Corp., a geodemographic research firm that has resliced the American pie into 40 different life style "clusters," from Blue-Blood Estates at the top (McLean, Potomac) to Hardscrabble at the bottom (poverty pockets in Appalachia). He stands in his ninth-floor Rosslyn office overlooking Georgetown, and he smiles a small but distinctly impatient smile at the thought of the old groupings. "They're not very sophisticated," he says. "They're not very useful."

Useful means useful to Claritas customers, ranging from The Coca-Cola Co. to Time Inc. to the AFL-CIO. These customers want to know who they can reach with their products and pitches--how to get the most bang for their advertising buck. By telling them how, Claritas had profits last year "in the fat seven figures," Robbin says. "We'll double that this year."

He paces around his office in a vested tweed suit and horn-rimmed glasses, digging maps and sheets of statistics out of an open-pit mine of paperwork. He is 52, a social scientist with degrees from Harvard and Columbia. He has worked for IBM, the Rockefeller Foundation and the Bureau of the Census. He is solid brio, capable of talking for 15 minutes at a stretch, all the while twirling a straight-back chair with one hand and spinning an old wooden swivel chair with the other.

He is talking about one of the more exotic assignments his company has handled.

Last year, the publishers of the Adam & Eve erotic novelties catalogue came to Claritas and handed over the ZIP codes of all their customers. They wanted to know to what kind of people they were selling their funny underwear and sex toys.

"We tried to guess what we'd get out of the computer," says Robbin. "We had a lot of surprised people. I figured it would be Cluster 37, which is Bohemian Mix. You know what it was? Cluster 8!"

Which is to say the type of neighborhood Robbin calls Money and Brains, for example, the neighborhood right across the Potomac from his high-rise office: Georgetown.

"And you know what?" Robbin exults. "There are two stores selling that stuff in Georgetown!"

It could be Brooklyn Heights, N.Y., Princeton, N.J., Grosse Pointe, Mich., or even a chunk of Hanover, N.H., Cluster 8s all of them.

Robbin waves his hand out the big window like an emperor who is delighted to show you his country. "With a Cluster 8 there's usually a college or university in there somewhere, and more than 20 percent of the households have incomes over $50,000 a year."

Claritas sales literature states: "These neighborhoods are typified by swank, shipshape town houses (some being private homes; some broken up into expensive flats) interspersed with mid-rise apartments on tree-lined streets. Cluster 8s are heavy consumers of adult luxuries--apparel, restaurants, travel and the like."

Like erotic novelties, in this instance.

Georgetown, a k a Money and Brains, a k a Cluster 8, is just one slice. The pie also includes: Pools and Patios, Shotguns and Pickups, Blue-Collar Catholics, Urban Gold Coast, Bunker's Neighbors, Grain Belt and so on--America divided into 40 different life styles, voting patterns, eating habits and ethnic mixes, all of them ranked and classified in literally thousands of different ways, from yogurt consumption to chain-saw usage to sewer hookups, whatever a Claritas customer is likely to want to know.

"Everybody used to say that you couldn't do effective geodemographic research on Americans because they moved so much. What we've proved is that they tend to find the same neighborhood wherever they go," Robbin says.

He likes to say you can move from Fairfield, Conn., to Stanford, Calif., and the only thing that changes is the palm trees. Not the people, the cars in the driveways, the liquor in the cabinet, the magazines on the coffee table. Birds of a feather become Claritas' sitting ducks, to use its phrase.

The point being: You are where you live.

"I broke out some figures on food in Georgetown," he says, rooting out a yellow legal pad. It bears long lists of foods: yogurt, frozen vegetables, dry/salted nuts--big in Cluster 8--and whipped toppings, dry cake mixes and powdered breakfast drinks--big in Cluster 19, which is called Shotguns and Pickups.

Shotguns and Pickups, as you might expect from the name, "leads the nation in ownership of mobile homes, and shows peak indices for large families with school-age children, headed by blue-collar craftsmen and operatives with high school educations," according to Claritas literature. Pylesville, Md., in Harford County, is a Cluster 19.

"Cooking for pleasure," Robbin says, with a laugh. "In Money and Brains they cook for pleasure at a rate of 116 percent of national average, but in Cluster 19, Shotguns and Pickups, they're at only 86 percent. There's an interesting correlation here between the cooking-for-pleasure figures and use of digestive remedies. Shotguns and Pickups uses a lot of them, and Money and Brains not so much. That's misleading, though, because the Shotguns and Pickups folks come from a tradition of greater reliance on home medicine. In Georgetown, everybody goes to the doctor."

Robbin can spiel off endless statistics on any of his clusters--what their members eat, where they go on vacations, what they drive. Tuna extender, jug wine, sports cars, Field & Stream magazine.

Any student of American life styles might come up with a lot of the same predictions. But Claritas, with 53 full-time employes, dozens of Apple II computers backed up by a mainframe IBM 3330 in Pennsylvania, and investment backing by Warner Communications, is doing it systematically. It started in 1971, when Robbin and Claritas took the computer tapes of the U.S. Census, and broke them down into more than a thousand bits of information about all of us, not by the conventional counties, but by ZIP codes. America is divided into about 36,000 ZIP code areas, each averaging 2,250 households and 6,300 people. Then they took that information and correlated it with 535 variables involving measures of education, wealth, size and age of family, mobility, ethnicity, type of housing and urbanization.

"It was a monstrous effort," he says. "Doing the census figures alone cost half a million dollars. Then there was a tremendous amount of data crunching after that."

They could have sliced the pie into as many clusters as there are people--demographers like to say that given the data base they can demonstrate that every man is indeed an island, unto himself--but the compromise was 40, from Blue-Blood Estates to Hardscrabble.

Each slice is ranked by what Robbin calls "zip quotient," or "a weighted composite of education and affluence variables," which is a nice way of saying class. Georgetown, as a Cluster 8, for instance, is No. 5 on the ZQ list. Blue-Blood Estates--Potomac or McLean--is No. 1. Shotguns and Pickups is 28.

And everybody lives in one of them.

What gets esoteric is the correlations. Robbin can order up a chart correlating, say, the popularity of the late news on television with almost anything he's got figures on from marketing research organizations. Late-news viewers, Claritas reports, are high on roll-on deodorants and dry soup mixes, but low on medium-size dogs and target shooting. Chainsaw owners read a lot of copies of Outdoor Life and watch the "Wonderful World of Disney." They do not read The New York Times, and they do not watch "Saturday Night Live." Advertising choices for a chain saw become clear. Advertisers might have guessed as much. But would they have known that they could reach a lot of likely buyers by mailing fliers to people who have mailed in guarantee cards for food freezers--people with English or Germanic names?

Claritas can draw maps of all of this: Computer-driven robot pens lurch around huge pieces of paper drawing ZIP code borders with a spectrum of inks. If you're looking for orange-juice drinking blue-collar Hungarians, Claritas knows where to tell you to look. Advertisers looking for super-affluent buyers can show their wares in a Time magazine VIP edition that goes to only select clusters.

Claritas can even draw what they call "The Mayonnaise Line" across the country, with people above it tending to eat tart-flavored salad dressings, and people below going for creamier mayonnaise dressings.

"We're doing political applications with two companies, one Democratic, one Republican," Robbin says. "In 1978, we were hired by the United Labor Committee of Missouri to fight a right-to-work initative that was on the ballot. We decided to spend almost nothing on television--we worried that it would bring our opponents to the polls when they might have stayed home. We came up with 18 different letters for different clusters we were trying to reach. We had telephone calls made to people we thought we could persuade. We ended up winning by a 59-to-41 margin."

One Claritas study showed that the memberships of of the American Civil Liberties Union, Common Cause and the National Organization for Women are virtually identical.

Robbin plans to expand the system once he can run the 1980 census tapes through his computers, thereby stratifying, dividing and segmenting America even further. A new class system! Is this a threat to the melting pot, and one nation indivisible, and the class-free society? If this system gets to be generally known, won't people resent being stereotyped?

"The beautiful thing about human beings is that they're all different," Robbin says. "All we do is predict where you can find more of one kind."

But what, for instance, if you live, say, in a chunk of southern Montgomery County called Cluster 20, or Young Influentials, whose major characteristic is that it's a junior-varsity Cluster 8, Georgetown with only half the incidence of people making more than $50,000 a year? Won't people in Cluster 20 be miserable until they get to trade up?

Robbin is very reassuring. "You're going to like it in Cluster 8," he says. "The theaters with foreign films, the shops . . ."

Even, perhaps, the erotic novelties.