Americans'obsession with jeans is beginning to wear thin.

Jeans long have been a goto staple in closets across the country. After all, not many pieces of clothing are so comfortable they can be worn daily, yet versatile enough to be dressed up or down.

But sales of the iconic blues fell 6 percent during the past year after decades of almost steady growth. Why? People more often are sporting yoga pants and leggings instead of traditional denim.

The shift is partly due to a lack of new designs since brightly colored skinny jeans were a hit a couple years back. It's also a reflection of changing views about what's appropriate attire for work, school and other places that used to call for more formalwear.

"Yoga pants have replaced jeans in my wardrobe," says Anita Ramaswamy, a Scottsdale, Arizona high-school senior who is buying more leggings and yoga pants than jeans. "You can make it as sexy as skinny jeans and it's more comfortable."

Tobe sure, the jeans business isn't dead: Customer Growth Partners, a retail consultancy, estimates denim accounts for 20 percent of annual sales at the nation's department stores.

But sales of jeans in the United States fell 6 percent to $16 billion during the year that ended in June, according to market research firm NPD Group, while sales of yoga pants and other "active wear" climbed 7 percent to $33.6 billion.

And Levi Strauss, which invented the first pair of blue jeans 141 years ago, is among jean makers that acknowledge their business has been hurt by what the fashion industry dubs the "athleisure" trend. That's led them to create new versions of classic denim that are more "stretchy" and mimic the comfort of sweatpants.

It's one of the few times jeans haven't been at the forefront of what's "trending". Businessman Levi Strauss and tailor Jacob Davis invented jeans in 1873 after getting a patent to create cotton denim work pants with copper rivets in certain areas like the pocket corner to make them stronger. By the 1920s, Levi's original 501 jeans had become top-selling men's workpants, according to Levi's corporate website.

Over the next couple of decades, the pants went mainstream. In 1934, Levi's took advantage of the rise in Western movies and launched its first jeans aimed at affluent women who wanted to wear them on dude ranches. Then teens boosted popularity of the pants, first among the greasy-hair-and-leather-jacket set in the 1950s and then the hippies in the 1960s.

Then in the 1970s and early 1980s, jeans became a status symbol when designers like Jordache rolled out more chic versions.

As a result of jeans' waning popularity, retailers and designers are focusing more on active wear and less on denim. For instance, J.C. Penney recently has doubled its selections in casual athletic looks and scaled back growth of its denim business.

It's too early to tell whether the new styles will help jeans regain popularity. Jennifer Romanello, for one, says she's not interested in them.

"If I want yoga pants, I will buy yoga pants," says the publishing executive from Rockville Centre, New York. "I just don't see jeans crossing the line to be yoga pants."