Don’t know your social ROI? You’re not alone. A study of 427 marketers at U.S. companies showed that 80% are still unable to quantify the value of their social media efforts. 87% of Fortune 500 companies can’t really tell you they got a new customer through social media. The why are we all doing this?

In 23 experiments conducted over the past four years and involving more than 18,000 people, study results are now out and were published in the spring issue of the Harvard Business Review. Far from disheartening, it gives marketers the push they need to use Facebook and all the social media channels better.

Social media does not work the way many of us think. Likes have little power. Even the endorsement of a brand does not affect a customer’s behavior or lead to a purchase – no matter who does the endorsing. What does work? Paid advertising exposed to those who have shown even mild interest in your brand by liking or following your postings.

While nearly every business large and small shifted to social media hoping they could reach sales goals by spending less money on advertising, turns out the (now not) “new media” is best utilized with the old methods of drawing in customers. Potential customers respond when hearing your best and most unique selling proposition in an ad and when hearing from your current users. Testimonials still hold the most power. If it’s from one of the prospect’s FB friends or family, it’s most likely to result in a purchase.