Within the US, among 44 ranking factors examined, social signals account for 7 of the 8 most highly correlated with Google search results, according to a new study from Searchmetrics. Presenting the correlations using Spearman’s rank correlation coefficient, the study determined that Google +1s (0.4) have easily the highest correlation, followed by number of backlinks, Facebook shares, and Facebook total (summary of shares, likes and comments), each at 0.34. Last year’s study, which looked at 21 factors, found social signals occupying 5 of the top 6 spots.
That social signals correlate with Google rankings is not news to search marketers. According to a recent survey from BrightEdge, 80% of search marketers believe social sharing of content will be either a much more (31%) or more (49%) important means to improve rank this year than last.
In the Searchmetrics study, other social signals correlating with Google rankings included Facebook comments (0.33), Facebook likes (0.31), Pinterest pins (0.29) and Tweets (0.28). (Google +1s and Pinterest pins were new to the study this year.) Still, the report cautions that social signals – as with other factors – cannot be said to be causal, but only correlated (i.e. well-ranked domains have many shares, +1s, etc.). Even so, the researchers cite studies suggesting that indexing is possible only through social signals.
Aside from social signals, backlink-related factors also continue to show up in the study as having a positive correlation with rankings. The number of backlinks was one of the highest-ranked factors, and other related factors found to have positive correlation included the proportion of nofollow links (0.25) and the proportion of backlinks with a stop word (0.18). The study notes that when combined with other factors, backlink factors tend to produce a very positive correlation.
About the Data: The report cautions that correlation does not equate to causation, and these results do not in any way guarantee that the factors have an effect on rankings or are even used by Google as signals.
Searchmetrics largely excluded specific navigational keywords (as was the case last year) from the original data pool, which included the top 10,000 keywords according to search volume, not wanting to distort the analysis. Search queries are considered to be navigational keywords if they return results, which are largely irrelevant and only return one exact match (for example: “Facebook Login”).
The first three pages of organic search results were always used as data pool. That keyword set covers approximately 90-95% of the data pool used in the study last year. Here, the researchers attempted to strike a balance between two factors, namely the preservation of the “greatest common denominator” as an optimal basis for comparison with last year’s analysis, and the consideration of new keywords that have emerged due to growth in search volume in the top 10,000.
The researchers note that their data pool is always kept up-to-date. Therefore, new, relevant keywords are used in current studies, such as, for example “Samsung Galaxy S4″ or “iPhone 5,” which did not even exist at the time of the 2012 study.
The 10,000 analyzed keywords led to:
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