• by Sarah Mahoney  @mahoney_sarah, July 27, 2014

As consumers become increasingly adept with their smartphones, physical retailers can expect to reap big gains. A new report from Forrester says that cross-channel retail sales in the U.S. are on track to reach $1.4 trillion this year, and predicts they will rise to $1.8 trillion by 2018.

These sales -- which it defines as transactions that are touched by any digital medium but not completed through the Internet -- are the result of people “preshopping” more frequently, and on more devices. Digital’s influence is so strong that these sales are now four times larger than online sales.

“We expect that online sales in the same time frame will reach $294 billion,” writes Forrester analyst Sucharita Mulpuru. “Together, online and cross-channel sales represent what Forrester calls web-impacted retail, which now comprises the majority (52%) of the entire retail pie. By 2018, we expect web-impacted retail to account for 59% of all retail sales.”

Of course, she notes, there is still tremendous variety by category. For example, in purchases like food and furniture, people are more likely to do extensive research online, “yet still want to touch and feel products before buying them.”

The average ratio of web-influenced offline sales to online-only sales is 5 to 1, the report says. Groceries have a 19 to 1 ratio, and event tickets, which typically require less research, has a ratio of only 9 to 10.

Retailers like Target and Walgreens have benefitted from investments in “supporting the in-store or “preshop” experience on mobile devices,” she writes, noting that 68% of online adults use their smartphones to check the Internet while they are in stores. Transactions on those phones, however, are still unusual: Although 48% of smartphone owners use their devices to shop, only 24% of them actually buy via phone.

The upshot for retail brands, she writes, is to continue to step up omnichannel effort. “At the moment, omnichannel primarily means inventory efficiency — having a real-time, accurate portrait of inventory across channels with the  ability to enable shoppers to buy in any channel and when it’s most convenient. Generally, that means investments in endless-aisle efforts, ship-from-store initiatives, and in-store pickup options.”

Still, that isn’t the end of the story, and inventory synchronization is just the beginning. “Efforts such as providing mobile-enabled points of sale,” she adds, “enabling store associates to send and receive text messages, and allowing remote customer service are revolutionary ways for retailers to support customers while also coping with higher cost structures, such as higher minimum wages.”