Consumers worldwide will spend nearly $3.46 trillion online in 2019, up from $2.93 trillion in 2018, according to the forecast from Internet Retailer, a Digital Commerce 360 brand. The expected 17.9% year-over-year growth in global web sales would be a slowdown from the 20.7% jump last year. However, global web sales are still growing faster than the more saturated U.S. ecommerce market, which Internet Retailer projects will increase 14.0% in 2019.

Global retail sales through all channels are likely to hit $21.00 trillion by the end of the year, a 3.4% uptick from $20.31 trillion in 2018, according to Internet Retailer estimates. This would increase online’s share of total retail sales to 16.4%, and ecommerce would account for more than three-quarters of overall retail gains.

As online revenue continues to grow each year, larger gains are necessary to achieve the same level of growth, so some deceleration makes sense. Ecommerce penetration has steadily been on the rise—with online’s share of retail spend registering 10.5% in 2016, rising to 12.3% in 2017 and closing out 2018 at 14.4%, Internet Retailer estimates. The momentum will continue into 2019, with penetration north of 16.0%, according to Internet Retailer’s analysis.

The largest online retailers are powering this growth. In 2018, three of the top 10 global online retailers ranked by 2018 ecommerce sales (excluding sites operating exclusively as marketplace platforms) were web-only merchants. Their online revenue also significantly contributed to bumping up 2018’s ecommerce penetration. As web sales rise without an accompanying uptick in offline sales, online’s share of total retail sales grows.

As a whole, the top 10 hit $427.28 billion in ecommerce sales in 2018, up 22.5% from $348.91 billion in 2017. These retailers accounted for 14.6% of all global ecommerce sales in 2018. Here’s a look at how they fared last year.

The three retailers in the web-only contingent represented 61.8% of total online sales for the top 10 leaders in 2018. Collectively, Amazon.com Inc. (excluding sales of third-party sellers), JD.com Inc. and Vipshop Holdings Ltd. pulled in $264.04 billion in web revenue, up 22.2% year over year from $216.00 billion in 2017.

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