Moz's Domain Authority is requested over 1,000,000,000 times per year, it's referenced millions of times on the web, and it has become a veritable household name among search engine optimizers for a variety of use cases, from determining the success of a link building campaign to qualifying domains for purchase. With the launch of Moz's entirely new, improved, and much larger link index, we recognized the opportunity to revisit Domain Authority with the same rigor as we did keyword volume[1] years ago (which ushered in the era of clickstream-modeled keyword data).
What follows is a rigorous treatment of the new Domain Authority metric. What I will not do in this piece is rehash the debate over whether Domain Authority matters[2] or what its proper use cases are. I have and will address those at length in a later post. Rather, I intend to spend the following paragraphs addressing the new Domain Authority metric from multiple directions.
Correlations between DA and SERP rankings
The most important component of Domain Authority is how well it correlates with search results. But first, let's get the correlation-versus-causation objection out of the way: Domain Authority does not cause search rankings. It is not a ranking factor. Domain Authority predicts the likelihood that one domain will outrank another. That being said, its usefulness as a metric is tied in large part to this value. The stronger the correlation, the more valuable Domain Authority is for predicting rankings.
Methodology
Determining the "correlation" between a metric and SERP rankings has been accomplished in many different ways over the years. Should we compare against the "true first page," top 10, top 20, top 50 or top 100? How many SERPs do we need to collect in order for our results to be statistically