A combination of lower gas prices at the pump and the knock-on effects of slowing economic growth in China contributed to a global retail sales slowdown in 2015, but there is a bright spot in the gloom: e-commerce.

Online sales areexpanding faster than previously anticipated and are projected to increase by double-digit rates every year through 2019, according to a new forecast from independent research firm eMarketer. Led by China, the Asia Pacific region is expected to be the main engine of this growth.

In 2015, worldwide retail sales rose by 5.6 percent to $22.5 trillion, down from a 6.1 percent growth rate in 2014. E-commerce sales, by contrast, jumped by 25.1 percent, reaching nearly $1.7 trillion.

While online spending last year made up just 7.4 percent of global retail sales, eMarketer projects that e-commerce sales growth will outpace brick-and-mortar sales growth by a more than 3-to-1 margin from 2014 through 2019. At this pace, e-commerce sales by 2019 are expected to more than double to nearly $3.6 trillion, accounting for 12.8 percent of all retail spending.

With its rising consumer class and huge population of online shoppers, China is expected to play an outsized role in that growth. The report states that e-commerce sales in China will more than quadruplebetween 2014 and 2019. The country already leads the world in e-commerce, but by 2019, China’s e-commerce market will reach $1.97 trillion, making it 3.5 times larger than that of the U.S., according to the eMarketer forecast.