Any retail site knows that social media is their friend. Not only do sites like Facebook, Twitter, and Pinterest have the massive user bases to drive traffic, but they also have the opportunity to drive traffic based on the trust factor. If one of your friends recommends a product (as opposed to a typical ad), you’re much more likely to check it out. That’s the thought behind Facebook main advertising platform, the Sponsored Story (and why it’s crushing traditional ads).

But not all social media sites are created equal when it comes to driving retail traffic. That’s the message coming out of a a new study from RichRelevance. The ecommerce personalization company looked at over 700 million “shopping sessions” and found that Facebook is still the king, but Pinterest has one notable plus.

According to the study, Facebook drives the most traffic to retail sites – plain and simple. Facebook was found to drive 85.8% of online shopping sessions, followed by Pinterest at 11.3% and Twitter at 2.9%.

And shoppers that comes from Facebook stay on the site longer and come back more often. Facebook referrals stay for an average of 7 pages per session, compared to 4 with Pinterest and 3 with Twitter. Facebook-referred customers had a conversion rate of 2.63%, much more that shoppers who came via Pinterest and Twitter (.93% and 1.09%, respectively).

What Pinterest is really good at, they say, is sending big spenders to retail sites. The average order for a buyer referred via Pinterest was $168.83, compared to $94.70 (Facebook) and $70.84 (Twitter).

“Every social network promises a new way of connecting consumers with retailers and brands,” said Diane Kegley, CMO of RichRelevance. “However, the big take-away from our research is that not all channels in the social space are created equal.”

Check out their infographic on the study below:

[via AllFacebook]