Chicago ? Shoppers who endured long lines and sometimes-frigid temperatures spent only slightly more during their Black Friday shopping sprees than they did last year, according to data released Saturday by a research firm.

At the same time, their pajama-clad counterparts, a much smaller group that accounted for only a fraction of overall sales, shopped online from the warmth of their homes and dramatically boosted their spending.

More than a year after the economy’s collapse began rattling shoppers, industry observers said Friday’s shopping sprees offered a strong start to the holiday season.

“We have struggled for a long time and one of the ways for the economy to get going again is for the consumer to begin to spend more freely,” said Bill Martin, co-founder of research firm ShopperTrak, which released its sales figures Saturday. “And I think this is an indication they were willing to do that.”

Preliminary sales data from Martin’s organization, a Chicago research firm that tracks sales at more than 50,000 stores, showed shoppers spent $10.66 billion when they hit the malls on the day after Thanksgiving. That’s only 0.5 percent more than last year when Black Friday sales rose a striking 3 percent.

The traditional shopping spree — dubbed Black Friday because it often was the day when a surge of shoppers helped stores break into “the black,” or profitability, the full year — has marked the kickoff of holiday shopping for many consumers.

But its importance has faded in recent years as merchants started hawking the deep discounts usually reserved for that day well in advance.

For example, last year’s Black Friday spending grew from $10.3 billion to about $10.6 billion. But the overall holiday spending fell 4.4 percent as shoppers slowed spending as the holiday season went on.

Still, the day is often used as an important barometer of shoppers’ mindset: what kinds of items they’re buying and what kind of discounts will lure them.