Click-and-collect grocery is the fastest-growing online segment for Walmart Stores Inc., according to a new analysis.

Click-and-collect accounted for almost no e-commerce sales at Bentonville, Arkansas-based Walmart two years ago, but the category doubled in size from June 2016 to June 2017 and now makes up more than a quarter of all the company’s online sales, according to a Business Insider E-Commerce Briefing that utilized Slice Intelligence data.

“While the spotlight is often focused on Walmart’s e-commerce spending spree, its click-and-collect grocery strategy — which includes using geofencing to notify employees when customers are at the store to retrieve their orders and 24-hour kiosks that automate grocery pickup — is the fastest-growing online segment for the company,” according to the analysis.

The Slice Intelligence data cited in the analysis also found that grocery accounted for 26% of all of Walmart’s U.S. e-commerce sales in the second quarter of 2017, and that grocery sales made up more of Walmart’s e-commerce sale than Sam’s Club and sales combined.

“Grocery accounts for 56% of Walmart’s total sales, and, with the online grocery industry projected to be worth $100 billion by 2025, the company is intent on maintaining its position as the leading U.S. grocer,” according to the analysis.

Business Insider also reported that Walmart’s click-and-collect strategy has likely been successful because of the proximity of its stores to customers’ homes. Doug McMillon, Walmart’s president and CEO, has said there is a Walmart within 10 miles of approximately 90% of the U.S. population.