Holiday shoppers hit the Lenox Square Mall in Atlanta. (EPA/ERIK S. LESSER)

The holiday shopping season isn’t quite over for retailers, with millions of customers expected to hit stores and websites this week to redeem gift cards and to treat themselves to steeply discounted goods. But a new study has found that, so far, the holiday season has shaped up to be a relatively healthy one for the retail industry.

Retail sales were up 7.9 percent between Black Friday and Christmas Eve compared to the same period last year, according to MasterCard SpendingPulse, which studies transaction and survey data on purchases made with credit cards, cash and checks. That figure excludes sales of automobiles and gasoline.

MasterCard SpendingPulse found that e-commerce provided crucial momentum this holiday season, with sales up 20 percent in that channel. The strength in online shopping was consistent with many forecasts for the season, which predicted e-commerce would post greater sales growth than brick-and-mortar stores. And it reflects the shopping patterns from the season’s unofficial Thanskgiving-weekend kickoff: Brick-and-mortar stores saw a 10.4 percent dip in sales during that time frame, while online sales hit record levels on Thanksgiving, Black Friday and Cyber Monday.

It stands to reason that Amazon was a key beneficiary of the surge in online shopping this holiday season because of the company’s overall e-commerce market share. For example, a study by Slice Intelligence found that some 36 percent of total online sales on Cyber Monday were rung up by Amazon. Meanwhile, a poll conducted by CNBC this holiday season found that some 49 percent of shoppers say they “always” or “most of the time” browse Amazon when they shop online.  (Jeffrey P. Bezos, Amazon’s chief executive, owns The Washington Post.)

Indeed, the Seattle-based e-commerce company announced Monday that it added more than three million customers to its Prime membership program in the third week of December alone and said it shipped a record number of packages with Prime. The retailer said a its own hardware devices were among the best-selling products on its site this season, with the Fire tablet ranking as its biggest seller and the Fire TV Stick ranking as its third-biggest seller.

In addition to the strength in online shopping, MasterCard SpendingPulse found that furniture was a bright spot this holiday season. Sarah Quinlan, the head of market insights for MasterCard Advisors, said that solid spending in this category — which includes many big-ticket items — is a sign that consumers are plenty willing to open their wallets for purchases they’ve carefully researched.  In an interview before the release of this latest data, Quinlan said that furniture sales generally may be getting a boost from millennials as they form their own households.

Another encouraging sign for retailers in MasterCard’s data was its finding that apparel sales saw “high single-digit growth” during the season. Coming into the holiday rush, apparel sales had been soft at many retailers, with chains from Macy’s to Target to Dick’s Sporting Goods saying that unseasonably warm weather appeared to be keeping consumers from scooping up boots, coats and other cold-weather gear.  As warmer temperatures hung on throughout December, there were reports that apparel retailers were missing out on millions in clothing sales this holiday season.  However MasterCard’s data suggests that consumers ended up ponying up for clothing after all. MasterCard found that women’s apparel sales saw robust growth, while sales of men’s clothing declined, dragging down the growth rate for the category overall.

MasterCard said in its report that low gas prices were likely a factor in spurring consumers to spend more this holiday season.

The National Retail Federation found in a survey that 65.9 percent of holiday shoppers said they are planning to shop the week after Christmas, so retailers are continuing to try to squeeze more dollars out of them with big clearance sales.