Falling gas prices were behind last month's significant increase in retail sales, according to the National Retail Federation (NRF).

The organization said that the gains seen by businesses excluding automobiles, gas stations and restaurants-a “strong” 6.3% percent unadjusted over the same period last year and a 0.7% increase seasonally adjusted from August-were stronger than had been expected.

“As gas prices dipped, consumers had more disposable income to spend on other items, especially back-to-school necessities like clothing and sporting goods,” said NRF Chief Economist Rosalind Wells. “If September's sales are any indication, shoppers appear confident heading into the holiday season.”

The September growth was led by clothing and clothing-accessory stores, which saw sales rise 3% adjusted from August and an “impressive” 11.9% over last year, the NRF said. Sporting goods, book, hobby and music stores also saw strong growth of 1.1% from August and 9.1% over last year.

The NRF expects retail industry sales to increase 6.5% this year over 2005, with holiday sales for November and December predicted to reach almost $460 billion.