Cross-channel sales — also known as web-influenced sales or transactions that touch a digital medium, but are not completed on the Internet — are now more than four times larger than online sales alone and will reach $1.8 trillion by 2018. This is according to Forrester's just released five-year US cross-channel retail sales forecast. Offline sales — primarily web-influenced offline sales — will comprise nearly 75% of the $475 billion in US retail growth anticipated between 2014 and 2018. This growth in cross-channel sales can be attributed to US online consumers increasingly using their phones in retail stores to research products online. Retailers would be wise to see this growing trend as the new normal; if this is the first you’ve heard about your customers’ in-store mobile behavior, you’re already late to the game.

Despite frequent in-store research on the mobile device, the number of actual mobile transactions remains low. Consumers are more interested in using their phone in the “pre-shop” phase, be it searching for a product’s location, comparing prices, or checking online inventory. Many retailers, such as Target, have found it worthwhile to invest more in mobile services that meet customers’ needs in their pre-shop context rather than at the point of sale. Target has helped customers find specific items in its stores via its mobile app: A customer can create a shopping list within the app, which then maps that list onto the floor map of the customer’s Target store location, guiding them through the aisles from one item to the next.

Many US consumers now also expect store associates to be equipped with some kind of mobile device to check inventory or show them more information about products in-store. Omnichannel efforts like these will further boost cross-channel sales, as retailers investing in offering this kind of visibility to shoppers will meet a customer need while also driving incremental sales in stores.

eBusiness leaders seeking to grow in the mature retail environment — and not lag seriously behind — must focus on bolstering their cross-channel sales and dedicating energy within their organizations to executing on their omnichannel strategies, including mobile. Your customers already expect this from you. As the majority of retail sales will continue to happen in physical stores, invest in revolutionary cross-channel techniques, such as providing store associates with mobile-enabled points of sale and mobile messaging capabilities to keep your physical stores as strong as possible.