The leading analytics consultant of Moz Tom Capper has shared some results of the study devoted to the role of links in Google’s ranking and, therefore, SEO.

According to the author, links still do represent a useful source of information for Google’s ranking algorithm. At the same time the search engine also uses many other sources. Branded search volume is one of them.

This study takes a deeper look on how it compared with a link-based metric. It was decided to take Domain Authority as a metric for comparison.

Note. Branded search volume is the monthly regional search volume for the brand of a ranking site.

A note on correlation studies

The fact that Domain Authority (or branded search volume, or anything else) is positively correlated with rankings could indicate that any or all of the following is likely:

  • Links cause sites to rank well.
  • Ranking well causes sites to get links.
  • Some third factor (e.g. reputation or age of site) causes sites to get both links and rankings.

That’s not to say that correlation studies are useless. However, the author believes that we should use them to inform our understanding and prompt further investigation, not as the last word on what is and isn’t a ranking factor important for search engines optimization.


Capper used STAT to request a sample of 5,000 non-branded keywords for the US market. Images, answer blocks and similar results were excluded.

Then Spearman’s rank correlation coefficient was used. It is a process that involves ranking variables according to branded search volume for each keyword, then taking the average correlation across all keywords.


For example, for Keyword A, we have varying branded search volumes in the top 5 search results. This means that search volume and rankings could never be particularly well-correlated, even though the results are perfectly sorted in order of search volume. Moz’s study devoted to Google’s ranking factors avoids this problem by comparing the ranking position (the 2nd column in the table) with the column on the far right of the table — how each site ranks for the given variable.

In this case, correlating ranking directly with search volume would yield a correlation of (-)0.75. Correlating with ranked search volume yields a perfect correlation of 1.

This process is then repeated for every keyword in the sample (desktop and mobile versions of the same keyword were counted as two keywords). Then the average correlation is taken.

Defining branded search volume

Initially, evaluating branded search volume for every site in the sample was supposed to be easy. It would only require looking up the search volume for their domain minus its subdomain and TLD (e.g. «walmart» for

However, this proved to be deficient. Take these examples:

Are the brands for these sites «cruise», «wordpress» and «sd» respectively? Clearly not. To figure out what the branded search term was, each potential candidate from the URL was taken and analyzed.

These were the options for

  • Ecotalker
  • Ecotalker wordpress
  • WordPress

Then the highest search volume term for which the subdomain in question ranked first was worked out.

Here’s the main conclusion: branded search volume is better correlated with rankings than Domain Authority is.


However, there are a few other points of interest here. Firstly, neither of these variables has a particularly strong correlation with rankings — a perfect correlation would be 1. It was found that a correlation between Domain Authority and rankings was of 0.071, and a correlation between branded search volume and rankings of 0.1. These are very low results.

By comparison Moz’s study found a correlation of 0.26 between Domain Authority and rankings using the same statistical methods.

The difference is likely to be caused by the fact that Moz analyzed 50 web results per query, compared to top −10 results in this study. If true, this would imply that Domain Authority has much more to do with what it takes to get you onto the front page than it has to do with ranking in the top few results once you’re there.

Another potential difference is in the types of keyword in the two samples. Moz’s study has a fairly even breakdown of keywords.


In this study, on the other hand, the keywords were more skewed towards the low end (< 10 thousand).


However, according to the author, this doesn’t seem to be the cause of the lower correlation numbers.

Regression analysis

Another way of looking at the relationship between two variables is to ask how much of the variation in one is explained by the other. For example, the average rank of a page in our sample is 5.5. If we have a specific page that ranks at position 7, and a model that predicts it will rank at 6, we have explained 33% of its variation from the average rank (for that particular page).

Using the data above, the author constructed a number of models to predict the rankings of pages in the sample, then charted the proportion of variance explained by those models below.

It’s worth noting that despite the very low R-squareds, all of the variables listed above were highly statistically significant.

The really interesting thing here is that including ranked Domain Authority and ranked branded search volume in the same model explains barely any more variation than just ranked branded search volume on its own. Nearly all of the variation in rankings that we can explain with reference to Domain Authority we could just as well explain with reference to branded search volume. On the other hand, the reverse is not true. What do these data tell us?

There are two main takeaways for SEO here:

1. If you care about your Domain Authority because it’s correlated with rankings, then you should care at least as much about your branded search volume.

2. The correlation between links and rankings might sometimes be a bit misleading — it could be that links are themselves merely correlated with some third factor which better explains rankings.

There were also other smaller conclusions made during the study, particularly around how weak both sets of correlations were. This places even more emphasis on relevancy and intent, which presumably make up the rest of the picture.

«If you’re trying to produce content to gain links and brand awareness, it might not be very good at either. So you need to figure out what’s right for you and how to measure it. We aren’t saying that „links are dead“. We encourage you to be a bit more critical about how, why, and when they’re important. For example, they might be of increasingly little importance on the first page of results for competitive terms» — says Capper.

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