Specifically, each fan a business gains on Facebook leads to an average of 20 additional visits to that company's website in a year, according to new data from metrics firm Experian Hitwise.

"We are constantly asked, 'What's the ROI with advertising on Facebook?' and until now that has always been a difficult question to qualify precisely," wrote Robin Goad, research director for Hitwise U.K., in a on Thursday.

Those additional visits, in turn, generate extra sales both online and offline, Goad added.

Up to 54 Percent More Likely

To come up with its results, Hitwise took the top 100 retailers ranked in its Hitwise Shopping and Classifieds category and benchmarked visits to their websites against the number of fans they had on their respective Facebook pages.