Online grocery spending worldwide will more than double in the next five years, according to a new study.

Forrester Research says online grocery sales totaled about $150 billion and will rise to $334 billion in the next five years, according to a story on mediapost.com.

Online grocery is entering the “maturing” phase in South Korea, China, Australia and the UK, according to Forrester, but markets like the U.S., Germany, India, Brazil and Russia are still in the “beginning” stages of adopting online grocery sales.

In the middle are “growing” countries like France, Japan, the Netherlands, Denmark and Norway.

Online grocery sales accounted for 2.9 percent of all grocery sales worldwide in 2017, leaving room for huge growth, according to Forrester analysts quoted in the story.

According to Forrester, in addition to home delivery, click-and-collect, curbside pickup and delivery lockers, stores around the world are experimenting with “dark stores, which are small warehouses not open to the public; distributed warehouses; centralized warehouses; subscription models; express delivery with 60 to 90 minutes; and hyperlocal services that deliver groceries from a local store.”