As a regular blogger on SEOmoz, I’m very interestin what drives traffic to our posts. Of course, there’s the usual realm of referrers and keywords, but lately I’ve been curious about how social signals (including Google’s new +1) correlate with traffic. In other words, how much more traffic will a post get because it gets more Tweets, Likes, or +1s?

So, I set out to do an informal correlation study, looking at how Tweets, Likes, +1, and our own internal social metrics – Thumbs Up and Thumbs Down – impact Unique Pageviews (UPVs) over two sets of data. The first set is the Top 50 posts (by UPVs) for the first half of 2011. The second set is all main-blog posts after the launch of Google+.

(1) Top 50 Posts of 2011
The first study was pretty straightforward. I looked at the traffic for all main-blog posts (including promoted YOUmoz posts) from January 1st to June 30th of 2011 and pulled the Top 50 by Unique Pageviews. For each post, I gathered data on Thumbs Up, Thumbs Down, Tweets, Likes and +1s, and calculated their correlations with UPVs. The graph below shows the correlations:

Correlations for Top 50 posts

Just a quick refresher – the correlation coefficient (r) varies from -1 to 1, with 0 indicating no relationship and 1 being a perfect positive correlation (when one variable goes up, the other variable goes up). Correlation does not imply causation, but I’ll get into the details of that below, because it’s very interesting for this data set. All values with Brazil Business Fax List asterisks (*) were statistically significant (p<0.01). Finally, I’d like to give a shout-out to our resident stats guru, Dr. Matt Peters, for working through the math with me.

Low, and thumbs down didn’t seem to encourage or discourage views, but neither of those measures were

(2) All Posts Since Google+
The +1 data in the first study is surprising, since Google+ didn’t launch until June and the button wasn’t implemented for most of the first half of the year. Many of these +1s arrived well after the original posts were published.

So, I ran a second study, using only blog posts EF Leads published between June 18th (the launch of Google+) and August 15th. This amounted to 44 posts, not too different a sample from the first study. Although the +1 button rolled out prior to Google+, I felt the roll-out date was a good cutoff, since that’s when people really took notice.