FRISCO, Texas — They are one of the most lucrative sectors in the retail industry, generating billions of dollars in sales, and arguably are the most underpublicized: the kiosks and carts that dot the aisles of big shopping malls, selling everything from candles to computers.

These freestanding merchants are tremendously popular — Tillie Martinez says she sometimes has customers lining up 10 and 12 deep to buy her personalized Christmas ornaments at Stonebriar Centre mall north of Dallas. And while she sells just a few months a year, she has a loyal following.

"The fun part is getting the repeat business from someone who last year bought something for their baby's first Christmas," she said.

Carts and kiosks are a thriving industry, bringing in an estimated $10 billion in annual sales for the merchants and landlords, more than triple that of 10 years ago, industry analysts said.

Marshal Cohen, senior industry analyst at NPD Group Inc., a market research company based in Port Washington, N.Y., said the kiosks are changing mall dynamics.

A kiosk "removes one of the biggest barriers and that's the entrance and walls to the stores," he said. "The mall owners tell you they are trying to enhance the consumers' shopping, but they are trying to maximize square footage as best they can, no question about it."

The kiosk concept relies on nostalgia for some of their appeal, allowing shoppers to revisit long-gone marketplaces where push cart merchants sold their wares, spending time face-to-face with each customer. But behind the sentiment is solid business strategy — some of the merchants are small businesses looking to expand or try out new ideas, while others are Fortune 500 companies looking to strengthen their foothold in a national market.

Some kiosks and carts are operated throughout the year, but at this time of the year, there's a population explosion of these merchants at malls. Hickory Farms, the Maumee, Ohio-based company known for its sausages and cheese, goes from one year-round store to 542 kiosks plus another 176 stores for the holidays.

Martinez opened her 4-foot-by-6-foot cart in October — one month earlier than last year — and is running it seven days a week until Christmas. She relies on her SUV for office and inventory space, while her cart is stocked with items priced from $9.95 to $21.95. Through November, she was $6,000 ahead of last year's pace.

For Austin-based Despair Inc., which posted $4 million in online sales of posters and calendars with pessimistic sayings, the carts are a source of additional revenue and exposure. Co-founders Lawrence Kersten, and brothers Jef and Justin Sewell agreed to have their father, Doug Sewell, start a separate company, the Sewell Group, to oversee the cart business.

Now in its first year in malls, the company opened three carts in San Antonio malls and four in Dallas.