Sales on the day after Thanksgiving rose to $10.6 billion, according to preliminary figures released Saturday by ShopperTrak RCT Corp., a Chicago-based research firm that tracks sales at more than 50,000 retail outlets.

Last year, shoppers spent about $10.3 billion on the day after Thanksgiving, dubbed Black Friday because it was historically the sales-packed day when retailers would become profitable for the year.

While it isn't a predictor of overall holiday season sales, Black Friday is an important barometer of people's willingness to spend during the holidays. Last year, it was the biggest sales generator of the season.

But experts caution that this year's sales growth may be hard to sustain for the remainder of the holiday shopping season, which has 27 days between Thanksgiving and Christmas instead of the 32 last year. Still, the sales boost was surprising in light of data showing shoppers are scaling back on discretionary spending because of a recession fueled by uncertainty related to turmoil in the world's financial and credit markets.