The holiday shopping season got off to a surprisingly solid start, according to data released by a Chicago research firm. But the sales boost during the post-Thanksgiving shopathon came at

the expense of profits as the nation’s retailers had to slash prices to attract shoppers in a season expected to be the weakest in decades.

Sales the day after Thanksgiving rose 3% to $10.6 billion, according to preliminary figures released by ShopperTrak RCT Corp., which monitors more than 50,000 retail outlets. Many observers

had been expecting consumers to spend more time browsing than buying.