BUFFALO, N.Y. -- Consumers may have shown some initial enthusiasm in the first official weekend of holiday shopping, but that doesn't necessarily mean they'll be clogging up stores for the rest of the season. The day after Thanksgiving, known as Black Friday, drew an estimated 147 million shoppers, up 4.8% over the year before, according to the National Retail Federation. Another industry tracker, ShopperTrak, estimated that Black Friday sales grew 8.3%, while sales on Saturday rose 5.4%. But the average spending per customer was down 3.5%, reinforcing concerns that the holidays will generate only a modest jump in sales. The National Retail Federation is expecting a 4% sales climb for November and December combined, the smallest increase for the industry since 2002. The trade group maintained its cautionary tone for the holidays after the big shopping weekend. "Though Black Friday weekend was a complete success for many retailers, the results of the holiday season won't be determined until the last two weeks of December," said President and Chief Executive Tracy Mullin in a statement. Retail stock trading Monday reflected this moderate view, with shares of most big chains losing steam after rallying Friday. Target ( TGT), which jumped 5.7% Friday, recently was down 2.2% to $55.92. Likewise, Circuit City ( CC) was shedding 4.2% to $6.24 after soaring 19% the prior session.