America, with its glamorous image of cowboys and rock stars, gave jeans to the world, but now denim is suffering from the blues.

Domestic sales of jeans dropped 6 percent last year, worrying some manufacturers and prompting VF Corp, the maker of Wrangler and Lee brand jeans to set up a think-tank to come up with other ways of using the distinctive and hard-wearing dyed blue cotton twill.

Thirty years ago, actress Brooke Shields famously said nothing came between her and her Calvin Klein jeans. Nowadays, young women can't seem to get far enough away from denim and even guys are forsaking the pants that became the uniform of several post-war generations.

Even Levi Strauss & Co, a name synonymous with jeans, is struggling, with second-quarter revenue dropping 2 percent from last year and net profit falling a whopping 76 percent because of falling sales in the U.S. It also cut 800 jobs -- 20 percent of its non-retail and non-factory positions -- as part of a plan to save up to $200 million a year.

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"A 6-percent drop may not seem like much, but it's rare for denim to take such a dramatic drop. It's a commodity business, we buy it and replenish it all the time."

A growing trend in casual wear is all about comfort, and denim is struggling to find its place. Retail and fashion experts alike are not afraid to admit the new look, coined "athleisure," is all the rage from teens turning to leggings instead of jeans and moms sporting their yoga-wear everywhere and all day long.

"There isn't an 'it' item for back-to-school like we had two years ago," said Dana Telsey, CEO and chief research officer at Telsey Advisory Group. "What there are, there are certainly dusters and dresses, there's these crop tops that seem to be working and anything with the athletic bent. Athletic and activewear are certainly the new everyday wear and that's happening no matter what age people are."

So is denim suffering a slow death or is it just a victim of fickle fashion trends? Only time will tell. Jean sales are down 6 percent year-over-year, according to NPD Group and retailers have taken notice.

"A 6-percent drop may not seem like much, but it's rare for denim to take such a dramatic drop. It's a commodity business, we buy it and replenish it all the time," said Marshal Cohen, chief industry analyst of The NPD Group.

VF Corp has noted the decline, with Scott Baxter who heads the company's jeanswear business, recently saying that its Lee brand, with a 60:40 ratio of women-to-men sales suffered a decline of about 15 percent in the United States. Interestingly, Wrangler, with only 20 percent of revenue coming from the women's category, saw a single-digit increase in the Americas.

Baxter told investors that In the Americas, the jeanswear business was facing continued challenges "due to the ongoing unfavorable women's denim trend."

Denim innovation center

To combat the denim doldrums, VF Corp said it will soon open a "global denim innovation center," but declined to give further details.