Online retail sales increased 20% between Black Friday and Christmas Eve, while total retail sales excluding automobiles and gasoline rose 7.9%, according to data released today by MasterCard Advisors.

MasterCard’s data shows that furniture and women’s apparel sales posted double-digit increases, accounting for a large chunk of the growth. MasterCard did not break out specific sales figures. Warmer fall weather delayed clothing and accessories sales to beyond Black Friday, and consumers tapped the money they’ve gained from cheap gas prices to buy during the holidays, spending 72 cents of every dollar they saved from lower fuel costs, MasterCard found. Some retail categories declined compared with last year, including men’s apparel, electronics and luxury items.

The 20% year-over-year jump in holiday e-commerce sales is higher than the 14% increase in e-commerce sales predicted by comScore Inc., which measures consumers’ web activity. But consumers report doing more research online, so the transition from research to sale makes sense, according to MasterCard’s Omnishopper Guide.

The rise of e-commerce “is a solid indication of an empowered and savvy shopper. We’ll be watching to see if this behavior continues into 2016,” says Sarah Quinlan, MasterCard Advisors’ senior vice president of market insights. The company’s data is based on national U.S. retail sales across all payments types between Nov. 27 (Black Friday) and Dec. 24. Part of the online sales increase during that period can be attributed to consumers lacking time and knowing they can buy a gift that someone wants, get it delivered and, if it doesn’t work out, the recipient will handle the return, Quinlan says.

“I don’t believe this kind of growth is sustainable, and I think we’ll see a return to more single-digit growth numbers after the first of the year,” she says. “Even with the surge in online spending growth, it’s still only 10% of total retail sales during this holiday period, so the share is still not huge. Consumers are doing their homework online and not necessarily executing there. “

The National Retail Federation in October predicted that retail sales during November and December will grow 3.7% compared with 2014 and that non-store sales—which include online and mail-order catalogs, telephone sales and other direct-to-consumer sales that do not take place online—will grow 6-8% over last year. An NRF survey, also from October, indicated online shopping will account for almost half of purchases this holiday season. Consumers, on average, said 46% of their holiday shopping this year will be done online, up from 44.4% in 2014, the survey said.

Black Friday and Cyber Monday were the largest U.S. online sales days this year, with $2.74 billion and $3.07 billion in retail purchases, respectively, according to the Adobe Digital Index. E-commerce spending measured only on desktops on the second Monday of December, which some call Green Monday (Dec. 14 this year), was $1.408 billion, up 31.6% from $1.070 billion in sales logged on Dec. 15, 2014, according to comScore Inc.