Pinterest accounted for 24.3% of all social network-driven transactions for AddShoppers’ more than 10,000 retail clients last year, according to a recent report from the social commerce platform vendor. That’s more than Facebook (24.2%), Twitter (20.9%) and Google Plus(6.6%). E-mail (19.2%) and assorted other social networks (4.9%) make up the remaining share of revenue. The percentages don’t add up to 100% because of rounding.

AddShoppers—which offers tools that enable retailers to add social features like social logins andsocial sharing buttons, along with social-oriented analytics tools—attributes social network-driven transactions based on shoppers clicking on an AddShoppers-shared link on a social network to a retailer’s site and making a purchase, or clicking away and buying that same item within the next 30 days.

Pinterest’s large share of overall revenue means that retailers should be trying out ways to leverage the social network, says Jon West, AddShoppers CEO. “Pinterest last year passed the threshold of being something new and interesting to a tool that should be a mainstay in retailers’ marketing mix,” he says.

Even so, only 77%—387 retailers—of the merchants in the Internet Retailer 2013 Top 500 Guide use the platform. And only 62%—308 retailers—feature the social network’s Pin It button on their sites, according to Top500Guide.com. The Pin It button enables shoppers to “pin” a product to a Pinterest board, or collection of images, with a single click from the retailer’s site.

Some retailers like pet supplies merchant PupLife.com that are active on Pinterest say the social network is especially effective at driving direct e-commerce sales. More so, even, than Facebook. “Facebook brings traffic to PupLife, but not a lot of customers,” says president Eric Houtkooper. “Pinterest is bringing both traffic and customers to PupLife and that is where we see significant growth potential for 2014. Customers who visit us from a product photo on Pinterest are already ‘pre-qualified,’ meaning they have seen already viewed the item in a positive manner and like what they see. We maintain an active Facebook presence to help bolster the brand and connect with our community, but we see Pinterest as the best social network for promoting our products for the year ahead.”

PupLife gets a total of 3.87% of its site traffic from social networks—2.07% from Pinterest alone—earning it the No. 241 spot in the Internet Retailer 2014 Social Media 500, which ranks the leaders in social commerce by the percentage of web site traffic they receive directly from social networks

As a whole, the 260 merchants active on Pinterest and ranked in both the 2013 edition of the Social Media 300 and the 2014 Social Media 500 grew their combined number of followers by around 220%, to 22.4 million from 7.0 million, according to analysis of new social data on Top500Guide.com.

This is not surprising, as Pinterest itself has been increasingly focused on making its platform more user-friendly for both retailers and consumers looking to shop. The social network last year introduced “product pins(More on product pins: )” that show users more information about the items for sale that shoppers “pin” in the network, such as where they can buy a product, its price and availability. And in November it introduced an API, or application programming interface—a set of software instructions for transferring data between programs—that lets merchants show shoppers the most recent items on their sites that Pinterest users pinned, the most clicked-through pins on their sites and pins from specific search terms. Wal-Mart Stores Inc. and Target Corp., Nos. 145 and 295 in the 2014 Social Media 500, were among the first retailers to use the API.

Even though 113 retailers in the 2013 Top 500 Guide don’t use Pinterest, most merchants West talks to understand that some merchants are succeeding on Pinterest. Far fewer recognize the potential value of Google Plus, he says. While Google Plus isn’t a huge driver of traffic for AddShoppers’ retail clients—it accounted for only 9.7% of traffic to client sites from social networks in December 2013—the average order value for the sales it drove was $171.98, more than Facebook ($128.48), Twitter ($105.69) and Pinterest ($139.72).

Google Plus is more important for some categories than others. For example, Google’s social network accounts for 15.3% of social traffic for AddShoppers’ B2B retail clients, but only 5.9% among the vendor’s apparel and accessories clients. That shows that retailers have to test to determine which social networks are most effective for their business, West says.

“Retailers have to measure this stuff,” he says. “They have to understand how to value different social networks.”

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