An annual survey of consumers' online buying behavior released today found that 51 percent of the roughly 5,000 respondents made all of their purchases on a digital platform during January and February, the first time in the survey's five-year history more than half did not buy anything in traditional stores.

The survey, conducted by research firm comScore Inc. and commissioned by Atlanta-based UPS Inc., found that 17 percent of the respondents said they planned to shop less in traditional stores.

However, UPS emphasized that physical stores still play a vital role in supporting the consumer buying experience.

Half of shoppers who bought online had their goods shipped to a physical store, the survey found. Of these, 46 percent made additional purchases while picking up their items, according to the survey. About 60 percent of respondents preferred to return items to a store, and 70 percent said they make additional purchases at that time. However, only 36 percent said they encountered helpful store associates when returning items to a store.

"Shoppers may be buying more online, but they still value the physical store," Teresa Finley, UPS' chief marketing officer, said in a statement. "Providing an exceptional in-store experience can position the retailer to convert more sales and enhance loyalty when customers pick up and return items."

As store-only purchases decline in frequency, the use of mobile devices continues to ramp up. The respondents' use of smartphones to shop has risen by 10 percentage points over the past two years, according to the survey. Consumers are using their phones to perform a wide range of functions, ranging from price comparisons to product reviews to accessing coupons for in-store redemptions, the survey found.

Consumers reported having a better shopping experience with mobile devices this year than they did in 2015, the survey said.

The survey, which has been conducted during the first quarter of each year, found that free shipping continued to be the most important factor in a consumer's decision to complete an online transaction, although respondents said they were willing to pay for faster deliveries. Though the residence continued to be the preferred delivery location, an increasing percentage of respondents said they were willing to receive packages at alternate delivery locations.

About 35 percent of respondents said they began their online searches at marketplaces like Amazon.com Inc. and e-Bay, Inc. according to the survey. The survey found that 15 percent have visited "showrooms without inventory" which allow customers to examine products at a physical location before ordering them online.

So-called cross-channel transactions, which refer to such actions as buying online and picking up at a store, accounted for 38 percent of all purchases, up slightly from a year ago. Meanwhile, store-only searches and purchases declined slightly, to 20 percent of purchases.

UPS said retailers must create "seamless experiences that resonate" with how their customers shop today. Having online access to store inventory is perhaps the most critical feature, according to the survey.