David Shaw wears long pants to protect his shins when he's skateboarding, or if it's rainy or very cold. Or for a special event, such as his eighth-grade graduation last Wednesday.

Otherwise, forget it.

"The only other time I wear pants is if all my shorts are dirty," said the 14-year-old resident of Newport Beach, Calif., shopping with his mom and little brother at the Metro Point shopping center in Costa Mesa recently.

As if retailers needed more trouble, teen-age boys are spending less these days on long pants, content instead to buy shorts or simply keep wearing — and re-wearing — the same old jeans and cargo pants.

Sales of pants for teen-age boys fell more than 10 percent and jeans sales dropped almost 15 percent in the 12 months ended April 30, according to market research firm NPD Group. By comparison, men's apparel sales rose about 4 percent, to nearly $52 billion in the same period.

Pants sales are more important than shorts sales for retailers because they typically cost more and have a higher profit margin. Moreover, pants are sold year-round and are considered a more stable part of a retailer's business, industry experts say.

J.C. Penney Corp.'s Web site sells shorts from $9.99 to $21.99; pants are $19.99 to $34. At The Closet, a trendy specialty store at Triangle Square shopping center in Costa Mesa, a guy can pick up a pair of shorts for $34 or spend $200 on a pair of Diesel jeans.

Some apparel retailers that have been offering upbeat financial reports of late -- including Hot Topic Inc., Pacific Sunwear of California Inc. and Gap Inc. -- acknowledge that getting guys to buy long pants is a challenge.

In fact, for Anaheim-based PacSun, currently one of retail's brightest stars, it has become a three-year headache.

"The drought of three years is longer than any of us has seen in our careers," said Pacific Sunwear President Tim Harmon, a retail industry veteran.

At the root of the problem is a shortage of tempting trends, apparel experts say.

"The malaise is really industrywide," said Elizabeth Pierce, an analyst with Sanders Morris Harris Inc. in Los Angeles. "Most companies will tell you they don't see any light at the end of the tunnel, because there's been nothing new in men's bottoms for a couple of years."

Designers and merchandisers for apparel manufacturer Tarrant Apparel Group recently visited nearly a dozen retailers, including JCPenney, Kohl's and Aeropostale, and discovered a sort of void in the men's pants market, said Gerard Guez, chief executive of the Los Angeles-based company.

"There was not a single store not crying for help to figure out the casual side of the men's business," he said.

Teen pants sales will become increasingly important for retailers in the coming months, as they begin stocking stores with back-to-school merchandise.

Yet young males' ho-hum attitude about buying pants probably is exacerbating retailers' problems.

"A guy can wear the same pair of pants five days in a row," said Marshal Cohen, senior retail analyst at NPD Group. "He couldn't care less."

And without a "must-have" trouser style to refresh their wardrobes, young men won't be compelled to shop.

"We've been cargo-panted to death," said David Wolfe, menswear expert and creative director of Doneger Group, a New York fashion trends consulting firm.