This weekend, Will Falls decided to skip the local mall near Raleigh, N.C., and shop online instead.

"No standing in line, no finding a parking spot," he says. "Just get comfortable and go at it."

Millions of Americans did the same — Falls helped contribute to an 8.5 percent increase in online shopping Monday compared with 2013, according to data from IBM.

That growth stands in contrast to an 11 percent drop in sales reported by the National Retail Federation at brick-and-mortar stores over the Black Friday weekend compared with a year ago.

"I definitely believe there is cannibalization occurring from the perspective of online against the stores," says Bob Drbul, an analyst and managing director at Nomura Securities.

Of course, some of that cannibalization is going to the retailers' own online arms, he notes.

As for how consumers shopped online, most used desktop computers, which accounted for three-quarters of online sales — though the use of mobile devices rose sharply.

Another reason for the drop in in-store shopping this past weekend, Durbl says, is that retailers spread their Black Friday sales across the whole month of November.

Elle Phillips, a graphic designer from near Boise, Idaho, had family members visiting for Thanksgiving this past weekend. They took very different approaches to their holiday purchases, she says.

"They wanted to go Black Friday shopping," says Phillips, 37. "I prefer to avoid it at all costs."

Her brother-in-law headed for the hunting and camping retailer Cabela's at 4 a.m., Phillips says. He came back six hours later, with tales of a checkout line stretching to the back of the huge store.

"It literally took him two hours just to get through to the register with a couple of hoodie sweaters," Phillips says. "So that just sort of ... verified the reason why I don't go out on Black Friday."

Phillips, meanwhile, did her shopping online, including finding some new Doc Marten boots for her husband. She looked first for the best price on Amazon, "and then I actually went straight to the manufacturer's website ... and I found an equally good price there, all with free shipping."

That kind of price shopping and free shipping is forcing profit margins down for retailers, says analyst Drbul. But he expects a strong holiday season nevertheless.

A big reason is that falling gas prices are putting more money in consumers' pockets.

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