Americans are poised to spend $586.92 billion in retail ecommerce in 2019, with a year-over-year growth rate of 14.0%.

Ecommerce spending growth will be driven by a 2.6% gain in digital buyers (to 195.3 million) and an 11.1% gain in spending per buyer (to $3,005). "The data suggests that the US ecommerce market is nearing a saturation point as it grows more in line with that of the total internet population," said Andrew Lipsman, eMarketer principal analyst and lead analyst of our latest report collection “Global Ecommerce 2019.” "To keep growing at double-digit rates, future channel growth will increasingly rely on continued strong gains in the spending rate per buyer."

US digital buyer penetration will surpass 80% for the first time, climbing from 79.6% in 2018 to 80.5% of internet users this year. Every cohort between the ages of 18 and 54 will have digital buyer penetration of greater than 80%, with 25- to 34-year-olds owning the highest penetration at 89.6%. Those in the older millennial demographic, which represents nearly 40 million digital buyers and more than 20% of the digital buyer population, are especially important due to their propensity for new household formation when long-term purchasing habits are established.

The most underpenetrated digital buyer demographics are teenagers ages 14 to 17 (who may not have their own disposable income to spend online) and those ages 65 and older (who did not grow up with the internet and are less inclined to make purchases online).

Amazon Prime members represent a large and important segment of the US ecommerce market. We estimate the number of Prime users will grow 8.6% to 121.2 million in 2019, representing 65.5% of all digital buyers and significantly outpacing overall digital buyer growth. That said, growth in Prime users is decelerating—down from 20.0% in 2017 and 12.2% in 2018—as it attains a higher level of US market penetration. Growth rates will continue to fall over the next few years.

According to Q1 2019 research from Consumer Intelligence Research Partners, Prime members spend an average of $1,400 on Amazon each year, more than double that of non-Prime members ($600).

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