Facebook Inc. (Nasdaq: FB), operator of the world’s largest social network, rose after researcher ComScore Inc. suggested that marketers can use the site effectively to encourage users to buy products.

Shares of Menlo Park, California-based Facebook climbed 3 percent to $27.10 at the close in New York. Facebook has declined 29 percent since it started trading at $38 on May 18.

Companies marketing to Facebook users who have signaled they “like” a business or have mentioned a brand in a post can have a “a statistically significant positive lift on people’s purchasing,” ComScore said in a blog post. The findings counter a Reuters/Ipsos poll earlier this week that showed sagging interest in the site and a minority of users being influenced by advertising when deciding what to buy.

Facebook has faced investor concerns about its ability to leverage its more than 900 million users to boost advertising revenue fast enough to justify its valuation. The company has said its user growth is outpacing advertising gains as more people use smartphones to access the site.