America's long-lived passion for wearing jeans is taking on the look of a pair of Elmer Fudd overalls: durable, but slightly fading.
No, the $8 billion-a-year jeans industry, one of the most enduring success stories in apparel history, isn't being eclipsed by a sudden craving for khaki or a new twill trouser. But there appears to be a slackening in the explosive growth in the number of people wriggling into dungarees, which began in the 1960 s.
A record 612 million jeans were sold in the United States last year - nearly three pairs for every person - up 5.3 percent from 1980. But this year analysts predict 10 to 15 million fewer dungarees will move off retailers' shelves, the result of shifting consumer tastes and simply too many pants chasing too few people.
''Jeans have become just another item of apparel,'' says Jay Meltzer, an analyst at Goldman, Sachs & Co., an investment firm. ''We do not see the demand for jeans disappearing from the face of the earth. But it is stabilizing.''
Moreover, the amount of denim shipped by US manufacturers dipped 14 percent last year from its peak in 1980, and could be down another 10 percent in 1982. (Roughly 80 percent of US-produced jeans are made of denim; the rest are corduroy or some other blend.)
The nation's blue-jean king, Levi Strauss & Co., which holds close to one-third of the market, saw unit sales drop 15 percent in the first half of 1982 from the same period last year. Earnings plummeted 51 percent. One reason is austere economic times.
''With the high cost of money today, people are reluctant to carry heavy inventories,'' says Tom Kasten, president of Levi's jeanswear division. ''That certainly has had a negative impact on our growth.''
Yet there are other reasons why jeansmakers probably won't see breakneck growth in dungaree sales in the future. For one thing, the members of the post-World War II baby boom that adopted jeans as their unofficial uniform are now reaching middle age.
To be sure, a number of jeansmakers have been successfully marketing new pants to the paunchier, middle-aged set. But industry analysts question just how many jeans the aging ''Pepsi generation'' needs hanging in the closet.
''The real population growth is coming in the over-25 age group,'' says one industry analyst. ''These people still wear jeans, but not as many.''
Beyond that, the industry has become a victim of its own popularity. A decade ago there was just a handful of dungarees to choose from, but more recently there have been literally hundreds of brands on the market. Hardest hit by the denim deluge have been the makers of status jeans.
In the past five years the number of people making designer jeans multiplied dramatically. They tried to follow in the footsteps of Calvin Klein and the three Nakash brothers, founders of Jordache Enterprises, who turned trim-tailored pants into multimillion-dollar empires. But the proliferation of designer brands only added to saturation problems in the jeans market. Their high cost - often around $30 a pair - hasn't helped sales, either.
Aided by some suggestive advertising, dozens of brands have entered the market, bearing inscriptions of everyone from TV villains (J. R. Jeans) to folk heroes (Willie Nelson's).
But today many people are going for dressier duds than jeans - even designer jeans. In response, companies have branched out into other casual, jeans-related lines in a variety of colors and fabrics (poplin and sailcloth, for instance). A number of companies have found other products to put their signatures on - everything from luggage to handkerchiefs.
Some designer jeans, such as Calvin Klein and Jordache, are still selling well, but the signatures on many other pants pockets are disappearing like invisible ink.
''Everybody and his brother was coming out with his name on jeans,'' says Kay Norwood, an analyst at Interstate Securities Corporation, a Charlotte, N.C., investment firm. ''The market simply got saturated with designer jeans.''
Still, any eulogy for the entire jeans industry may be premature. After all, people have predicted the demise of denim since it was first popularized in the '50s and '60s. Then came the bell-bottom, or the trim-tailored designer, or the Western craze, to rescue it.
''We don't see anything on the horizon that will change,'' says Mr. Kasten of Levi Strauss. ''In the 1970s, the growth in the jeans market was explosive. That growth has moderated, but it is still growing.''
Industry officials are banking on the current baby ''boomlet'' to produce another generation of jeans lovers. They also believe more can be done to meet the growing demand for jeans among women. Some overseas markets also look promising, particularly Brazil and Mexico. The East bloc, too, is seen as a potential denim stronghold.
''We don't see anything taking the position of denim,'' says Tom O'Gorman, president of the sportswear fabrics division of Burlington Industries, the world's No. 1 denim supplier. ''The markets are there. It is just a matter of time. There is absolutely nothing to indicate jeans have run their course.''