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Investors are taking shares of Amazon.com Inc. (NASDAQ: AMZN) down Friday morning after the company reported fourth-quarter earnings after markets closed on Thursday. The e-commerce giant beat earnings per share estimates, but revenues, both for the quarter and for the year, were below expectations.

The company’s full-year sales rose by a third, and fourth-quarter sales rose by nearly as much. Fourth-quarter sales rose phenomenally despite what can only be described as a middling quarter for most retailers.

Researchers at Slice Intelligence note that Amazon accounted for 43% of all U.S. online sales in 2016 and a startling 53% of all U.S. online sales growth. That’s in a year when e-commerce sales rose 24% in the United States. That is dominance.

How does Amazon do it? Slice attributes the company’s sales increases to growth in sales of electronics, which accounted for 18% of Amazon’s 2016 sales increase, and double-digit year-over-year growth in home and kitchen goods, apparel and accessories, food, and health and beauty goods.

The primary factor, though, according to Slice is Amazon’s amazing dominance in shipping speed. By December of last year, the average package from Amazon was delivered in 3.4 days, compared with an average of 5.6 days from everyone else. As the researchers noted, Amazon “maintains an obsessive focus on removing every pain point from the buying process.” And there is no bigger pain point than having to wait a week to get an order delivered.

Analysts will be making calls on the company’s ratings and price targets Friday, and don’t be surprised if they generally come down on the side of higher targets and perhaps even a few ratings increases.

Amazon dominates online retail in the United States in the same way that Google dominates search, and for Amazon at least, no single competitor has appeared that could have any chance of challenging that dominance.

In Friday’s premarket, the company’s shares traded down about 4%, at $806.35 in a 52-week range of $474.00 to $847.21. The stock closed at $839.95 on Thursday, and the 12-month consensus price target was $929.10 before the earnings report.