Amazon and eBay benefit from increased use of mobile devices for shopping because they are consistently the top two online retail destinations for mobile users, ChannelAdvisor's Wingo said.
Amazon.com was the most visited retail website on Black Friday, with more than 28 million visits, according to Hitwise.
Worth noting: eBay runs one of the largest online marketplaces, rather than being a retailer, so its online traffic was not reported by Hitwise. However, eBay said the volume of mobile transactions on its marketplace jumped 153 percent on Black Friday from a year earlier.
ChannelAdvisor clients' same-store sales on Amazon.com shot up 43 percent on Saturday, compared with a year earlier. Last year's year-over-year growth was 49 percent on the Saturday following Black Friday.
Client same-store sales on eBay's marketplace rose 36 percent on Saturday, compared with a year earlier. Last year's year-over-year growth was 12 percent, according to ChannelAdvisor.
While mobile devices may be good for sales, they may not be so good for retail profit margins. Smart phones give shoppers real-time access to product prices online, potentially exacerbating the usual holiday discounting and price wars.
Black Friday online transactions jumped almost 30 percent, but the average ticket price was down more than 11 percent, according to Chase Paymentech, which reports data from its 50 largest e-commerce merchant clients.
"It's driving prices down," Shernoff said. "Consumers are checking prices in stores and showing the retailer, and the retailer will succumb to the lowest price online so they don't lose the consumer."
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