As omnichannel shopping heightens, retailers could benefit from a cross-device perspective that allows them to track consumers’ purchasing journeys.

Criteo, a performance marketing company, released a report about cross-device measurement and the importance of taking a user-centric view of the purchasing journey. The company’s report indicated that a third of online transactions could be misattributed by marketers not implementing cross-device measurement because they’re not identifying the many devices shoppers use to begin and complete their transactions. Without a cross-device approach, companies won’t know how consumers are shopping, which translates into missed opportunities to market to them.

By understanding how consumers are shopping–via mobile apps, mobile browsers, computers, etc–Criteo says retailers can optimize their marketing dollars, maximizing ROI. Compared to a single device approach, the company says cross-device measurement can generate more accurate conversion rates, which in some cases can be 1.4 times higher than reported by a single device view.

By measuring across devices, retailers will also note that consumers view more products than traditional analytic tools suggest and that they are more likely to place items in the shopping cart before making a purchase. Considering 31 percent of all transactions involve two or more devices and that buyer journeys are 41 percent longer than partial-view models, retailers are missing out on opportunities to cater to their tech-savvy consumers.

Although consumers use computers, tablets and smartphones to buy items, the report found that mobile is gaining momentum as a cross-device category.

Last year’s mobile growth data indicated that 36 percent of U.S. online purchases were completed on a cell phone, which was a year-over-year increase of 20 percent. Smartphone spend also increased by 7 percent last year, meanwhile Criteo’s H1 2016 report said that mobile apps captured 55 percent of transactions compared to 45 percent for mobile browsers. Fashion and luxury retailers held the largest share of mobile transactions (41 percent) and sporting goods purchases experienced a 30 percent year-over-year increase in mobile transactions as well.