Dan Zarella has looked at the correlations between social sharing (on sites like Facebook, Twitter and LinkedIn) and inbound links.

Dan compiled a database of more than 25,000 URLs that had been shared at least once on the three major social networks (Facebook, Twitter and LinkedIn), were at least a month old, and had at least one incoming link. He’s summarised his research in a succinct and handy way:

First, I looked at the relationship between the number of times a URL was Tweeted and the number of incoming links it had pointing to it. I found a convincing positive relationship. Those URLs that got more Twitter love, also got more link love.

Secondly, I looked at Facebook and found, somewhat unsurprisingly, almost exactly the same effect. Facebook popularity is related to inbound link popularity for URLs.

Finally, I looked at LinkedIn sharing. Of course the numbers are much smaller here due to sharing activity being much more common on Twitter and Facebook, but I still found another positive relationship.

For all of the “big three” social media networks, I found that social sharing had a positive relationship to incoming links pointing to a URL. This result is basically what I expected to see. However, when I took a step back and compared the actual Pearson’s Correlation Coefficient of the sharing on the three networks to inbound links, what I found was surprising.

While all three networks did have a positive correlation, the strength of the relationship was strongest for LinkedIn. So, while LinkedIn may be the least obvious choice for sharing activity, it is still incredibly important for marketers also interested in SEO performance.

via New Data: The Correlations Between Social Sharing and Inbound Links | SEOmoz.