Apps are pulling their weight in sales for retailers that have them, according to advertising technology vendor Criteo SA.

Apps account for 66% of mobile sales for retailers that have both a shopping app and mobile website. Criteo’s data is based on browsing and purchasing data for more than 5,000 retailers in 80 countries in the fourth quarter 2017.

Here’s how e-commerce transactions broke down for retailers with an app and excluding those app transactions in the fourth quarter.

Apps generate such a large portion of mobile sales because shoppers are more apt to make a purchase from a product detail page in app versus on the mobile web, according to Criteo data from North American retailers in the fourth quarter. On the mobile web, 6% of product page viewers eventually make a purchase. In an app that rate is more than three times higher, with 21% of product page viewers eventually buying a product.

Excluding apps, mobile web sales for both smartphones and tablets were 35.5% of e-commerce sales in the fourth quarter of 2017 compared with 34.8% in the fourth quarter 2016 for U.S. retailers. And even though smartphones may not generate the majority of sales, Criteo finds that 26% of all desktop transactions are preceded by a click on a mobile device for U.S. merchants in the fourth quarter.

Sporting goods and fashion/luxury goods are the two retail categories with the highest share of mobile sales as a portion of e-commerce sales. Here’s how mobile web sales (excluding apps) stack up in the fourth quarter by category for U.S. merchants:

• Sporting goods, 44%
• Fashion/luxury, 40%
• Health/beauty, 38%
• Flowers and gifts, 35%
• Mass merchant, 28%
• Home, 23%
• High tech, 20%

For retailers that have stores, in-store only shoppers are about 49% of shoppers and generate 49% of sales. Online-only shoppers are about 44% of shoppers and generate 24% of sales, but omnichannel shoppers are only 7% of shoppers but generate 27% of sales of retailers, according to global Criteo data from November 2017.

Criteo also finds that smartphone and tablet sales are highest on nights and weekends, whereas desktop sales are highest during work hours during the week.