Online shoppers outnumbered their brick-and-mortar counterparts during U.S. retailers’ pivotal Black Friday weekend, underscoring the challenges facing American malls this holiday season.

More than 103 million people shopped online over the four-day weekend, which started Thursday, according to an annual survey commissioned by the National Retail Federation. That compares with fewer than 102 million who ventured into traditional stores, the trade group said.

The growth of e-commerce – including people using their smartphones to buy gifts – helped boost the total number of U.S. shoppers to more than 151 million over the weekend. That figure, which accounts for the overlap between online and offline buyers, topped the 136 million that the trade group had predicted. Other factors, including an earlier rollout of holiday promotions, also are changing consumers’ behavior, NRF President Matthew Shay said.

The industry is seeing “an evolutionary change in holiday shopping by both consumers and retailers,” Shay said.

Still, it’s hard to tell if consumers are spending as much as they once did. The average shopper shelled out $299.60 over the weekend, said the federation, which commissioned Prosper Insights & Analytics to conduct the survey. But a change in methodology means that figure isn’t comparable to those from prior years. It had been $380.95 in 2014’s Black Friday weekend and $407.02 the year before.

The NRF also didn’t provide a total spending amount, something it included in past surveys. That figure had been down for two straight years, dropping 11 percent to $50.9 billion in 2014.

The change in methodology made it difficult to tell if this is the first year that online shoppers exceeded the offline total. Most consumer spending remains solidly at brick-and-mortar locations. But given the faster growth rates in e-commerce sales, the retail industry appears to be reaching a turning point.

The ritual of Black Friday – the post-Thanksgiving day that has long marked the beginning of the holiday season – also has changed. Frenzied consumers still line up in front of stores to take advantage of deals on toys and televisions, but crowds were smaller at many U.S. malls Friday. The event is also seen as an opportunity for window shopping, rather than spending.

As more shopping shifts to the Web, Wal-Mart Stores Inc., Target Corp. and other traditional retailers are doing their best to ward off the e-commerce king: Inc. Target plans to offer free shipping on online orders this holiday season for the second year in a row. Wal-Mart, meanwhile, is encouraging e-commerce shoppers to take advantage of in-store pickup, an attempt to leverage its more than 4,600 U.S. locations.

The retail industry’s next test will be Cyber Monday, a day when e-commerce sites roll out more deals. The term Cyber Monday was coined a decade ago, when retailers noticed a spike in online holiday shopping on the Monday after Thanksgiving. The reason: Many people returned to work and used their office’s high-speed Internet connection to shop. These days, most Americans have broadband, decreasing the event’s relevance.