We know that Amazon (AMZN) is an e-commerce giant, putting others' online efforts to shame, but recent data shows that it's not just online retailers that are losing out.

During the fourth quarter, Amazon was responsible for more than 51% of all U.S. retail growth, according to Wells Fargo analyst Matt Nemer. The calculations are based on Wells Fargo's estimate for Amazon's North America Gross Merchandise Volume and the U.S. Census estimates for retail sales in relevant retail categories (excluding motor vehicle dealers, gas stations and fuel, and food and beverage).

"Amazon's share gains have continued to massively accelerate," Nemer wrote in a note Tuesday.

The analyst also estimated that Amazon accounted for 42% of all retail growth for 2015 as a whole, up from the 22% it generated in 2014.

Walmart (WMT) , on the other hand, is not so lucky. It has captured less than 7% of U.S. retail growth during the fourth quarter and 9% of the growth in 2015, according to Nemer.

These numbers shouldn't be too surprising, given the rising share of e-commerce in the retail industry and Amazon's dominance in e-commerce.

Consider that on Cyber Monday, Amazon accounted for 36.1% of all online sales, according to market research firm Slice Intelligence. The runner up, Best Buy (BBY) , only captured 5.5%. Walmart was responsible for 3.8%, Nordstrom (JWN) for 3.6%, and Macy's (M) for 2.8%.

At the same time, more shoppers are opting to buy online as opposed to venturing into bricks-and-mortar stores.

The latest figures from the Census Bureau show that e-commerce sales jumped 15.1% in the third quarter compared to the same time period in 2014, and made up 7.4% of total retail sales, up from 7.2% in the second quarter.

This past week, Amazon reported fourth-quarter revenue of $35.7 billion, up 22% year over year, and earnings of $1 per share. These numbers didn't quite live up to analysts' high expectations, however -- analysts surveyed by Thomson Reuters were looking for Amazon to earn $1.58 a share on $36 billion in revenue.

Nonetheless, it doesn't seem like Amazon needs to be too worried.

"Everyone is freaking about Amazon and that's because Amazon has decided once again that it wants to reignite spending in order to take over the world," said Jim Cramer, portfolio manager of the Action Alerts Plus Portfolio.

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