NEW YORK (CNNMoney.com) -- Halloween costume sales are projected to jump 50 percent this year as princesses, pirates and witches get set to go on the prowl on Oct. 31, according to the National Retail Federation.

The NRF, which represent the nation's big retailers, estimated $4.96 billion will be spent on costumes this year, making it the sixth largest spending holiday.

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That's up sharply from the group's forecast of $3.3 billion last year.

The holiday, traditionally celebrated by children, is gaining the attention of young as well as older adults, fueling the explosion in costume sales, the trade group said.

"When it comes to dressing for Halloween, traditional costumes never go out of style," NRF President Tracy Mullin said in a statement. "In order to please consumers of all ages, retailers have begun stocking their shelves with a wide variety of costumes, from classic favorites to pop-culture icons."

In its survey of about 8,000 consumers, the group found that nearly two-thirds of those polled plan to celebrate Halloween this year, up from the 52 percent last year, with more than a third planning to dress up.

The number of young adults joining in on the fun jumped for the second year in a row, with 85 percent of 18- to 24-year olds planning to take part in the celebration this year, up from 67 percent last year, according to the survey.

"Many retailers have altered their merchandise assortment to appeal to this enthusiastic consumer base," said Phil Rist, vice president at BIGresearch, a firm that polled consumers about their costume choices for the NRF. "[Retailers know] the competitive spirit that exists among young adults when it comes to sporting the best Halloween costume."

Overall, traditional costumes are still the most popular choice for kids and adults alike.

Among kids, the princess held her reign as most popular costume for the second straight year with nearly 4 million children planning to adorn tiaras, the trade group said, while pirates were popular with children and adults alike.

"This year pirate costumes are popular ... due largely to the widespread success of the 'Pirates of the Caribbean' franchise," Rist said in a statement.

Consumers have already begun the search for the perfect outfit as Yahoo! (down $0.40 to $24.88, Charts) Shopping reported Halloween costumes among the top 10 most-searched products.

Online costume stores will compete with Halloween supplier Party City (up $0.04 to $17.14, Charts) and discount stores Wal-Mart (down $0.88 to $48.44, Charts) and Target (up $0.57 to $55.82, Charts).

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