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 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 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.
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 significant? It’s important that I outline the methodology for reproducibility and for any comments or concerns on the techniques used. For the purposes of this study, I chose to use the “true first page.” This means that the SERPs were collected using only the keyword with no additional parameters. I chose to use this particular data set for a number of reasons:
- The true first page is what most users experience, thus the predictive power of Domain Authority will be focused on what users see.
- By not using any special parameters, we’re likely to get Google’s typical results.
- By not extending beyond the true first page, we’re likely to avoid manually penalized sites (which can impact the correlations with links.)
- We did NOT use the same training set or training set size as we did for this correlation study. That is to say, we trained on the top 10 but are reporting correlations on the true first page. This prevents us from the potential of having a result overly biased towards our model.
I randomly selected 16,000 keywords from the United States keyword corpus for Keyword Explorer. I then collected the true first page for all of these keywords (completely different from those used in the training set.) I extracted the URLs but I also chose to remove duplicate domains (ie: if the same domain occurred, one after another.) For a length of time, Google used to cluster domains together in the SERPs under certain circumstances. It was easy to spot these clusters, as the second and later listings were indented. No such indentations are present any longer, but we can’t be certain that Google never groups domains. If they do group domains, it would throw off the correlation because it’s the grouping and not the traditional link-based algorithm doing the work.
I collected the Domain Authority (Moz), Citation Flow and Trust Flow (Majestic), and Domain Rank (Ahrefs) for each domain and calculated the mean Spearman correlation coefficient for each SERP. I then averaged the coefficients for each metric.
Moz’s new Domain Authority has the strongest correlations with SERPs of the competing strength-of-domain link-based metrics in the industry. The sign (-/+) has been inverted in the graph for readability, although the actual coefficients are negative (and should be).
Moz’s Domain Authority scored a ~.12, or roughly 6% stronger than the next best competitor (Domain Rank by Ahrefs.) Domain Authority performed 35% better than CitationFlow and 18% better than TrustFlow. This isn’t surprising, in that Domain Authority is trained to predict rankings while our competitor’s strength-of-domain metrics are not. It shouldn’t be taken as a negative that our competitors strength-of-domain metrics don’t correlate as strongly as Moz’s Domain Authority — rather, it’s simply exemplary of the intrinsic differences between the metrics. That being said, if you want a metric that best predicts rankings at the domain level, Domain Authority is that metric.
Note: At first blush, Domain Authority’s improvements over the competition are, frankly, underwhelming. The truth is that we could quite easily increase the correlation further, but doing so would risk over-fitting and compromising a secondary goal of Domain Authority…
Handling link manipulation
Historically, Domain Authority has focused on only one single feature: maximizing the predictive capacity of the metric. All we wanted were the highest correlations. However, Domain Authority has become, for better or worse, synonymous with “domain value” in many sectors, such as among link buyers and domainers. Subsequently, as bizarre as it may sound, Domain Authority has itself been targeted for spam in order to bolster the score and sell at a higher price. While these crude link manipulation techniques didn’t work so well in Google, they were sufficient to increase Domain Authority. We decided to rein that in.
The first thing we did was compile a series off data sets that corresponded with industries we wished to impact, knowing that Domain Authority was regularly manipulated in these circles.
- Random domains
- Moz customers
- Blog comment spam
- Low-quality auction domains
- Mid-quality auction domains
- High-quality auction domains
- Known link sellers
- Known link buyers
- Domainer network
- Link network
While it would be my preference to release all the data sets, I’ve chosen not to in order to not “out” any website in particular. Instead, I opted to provide these data sets to a number of search engine marketers for validation. The only data set not offered for outside validation was Moz customers, for obvious reasons.
For each of the above data sets, I collected both the old and new Domain Authority scores. This was conducted all on February 28th in order to have parity for all tests. I then calculated the relative difference between the old DA and new DA within each group. Finally, I compared the various data set results against one another to confirm that the model addresses the various methods of inflating Domain Authority.
In the above graph, blue represents the Old Average Domain Authority for that data set and orange represents the New Average Domain Authority for that same data set. One immediately noticeable feature is that every category drops. Even random domains drops. This is a re-centering of the Domain Authority score and should cause no alarm to webmasters. There is, on average, a 6% reduction in Domain Authority for randomly selected domains from the web. Thus, if your Domain Authority drops a few points, you are well within the range of normal. Now, let’s look at the various data sets individually.
Random domains: -6.1%
Using the same methodology of finding random domains which we use for collecting comparative link statistics, I selected 1,000 domains, we were able to determine that there is, on average, a 6.1% drop in Domain Authority. It’s important that webmasters recognize this, as the shift is likely to affect most sites and is nothing to worry about.
Moz customers: -7.4%
Of immediate interest to Moz is how our own customers perform in relation to the random set of domains. On average, the Domain Authority of Moz customers lowered by 7.4%. This is very close to the random set of URLs and indicates that most Moz customers are likely not using techniques to manipulate DA to any large degree.
Link buyers: -15.9%
Surprisingly, link buyers only lost 15.9% of their Domain Authority. In retrospect, this seems reasonable. First, we looked specifically at link buyers from blog networks, which aren’t as spammy as many other techniques. Second, most of the sites paying for links are also optimizing their site’s content, which means the sites do rank, sometimes quite well, in Google. Because Domain Authority trains against actual rankings, it’s reasonable to expect that the link buyers data set would not be impacted as highly as other techniques because the neural network learns that some link buying patterns actually work.
Comment spammers: -34%
Here’s where the fun starts. The neural network behind Domain Authority was able to drop comment spammers’ average DA by 34%. I was particularly pleased with this one because of all the types of link manipulation addressed by Domain Authority, comment spam is, in my honest opinion, no better than vandalism. Hopefully this will have a positive impact on decreasing comment spam — every little bit counts.
Link sellers: -56%
I was actually quite surprised, at first, that link sellers on average dropped 56% in Domain Authority. I knew that link sellers often participated in link schemes (normally interlinking their own blog networks to build up DA) so that they can charge higher prices. However, it didn’t occur to me that link sellers would be easier to pick out because they explicitly do not optimize their own sites beyond links. Subsequently, link sellers tend to have inflated, bogus link profiles and flimsy content, which means they tend to not rank in Google. If they don’t rank, then the neural network behind Domain Authority is likely to pick up on the trend. It will be interesting to see how the market responds to such a dramatic change in Domain Authority.
High-quality auction domains: -61%
One of the features that I’m most proud of in regards to Domain Authority is that it effectively addressed link manipulation in order of our intuition regarding quality. I created three different data sets out of one larger data set (auction domains), where I used certain qualifiers like price, TLD, and archive.org status to label each domain as high-quality, mid-quality, and low-quality. In theory, if the neural network does its job correctly, we should see the high-quality domains impacted the least and the low-quality domains impacted the most. This is the exact pattern which was rendered by the new model. High-quality auction domains dropped an average of 61% in Domain Authority. That seems really high for “high-quality” auction domains, but even a cursory glance at the backlink profiles of domains that are up for sale in the $10K+ range shows clear link manipulation. The domainer industry, especially the domainer-for-SEO industry, is rife with spam.
Link network: -79%
There is one network on the web that troubles me more than any other. I won’t name it, but it’s particularly pernicious because the sites in this network all link to the top 1,000,000 sites on the web. If your site is in the top 1,000,000 on the web, you’ll likely see hundreds of root linking domains from this network no matter which link index you look at (Moz, Majestic, or Ahrefs). You can imagine my delight to see that it drops roughly 79% in Domain Authority, and rightfully so, as the vast majority of these sites have been banned by Google.
Mid-quality auction domains: -95%
Continuing with the pattern regarding the quality of auction domains, you can see that “mid-quality” auction domains dropped nearly 95% in Domain Authority. This is huge. Bear in mind that these drastic drops are not combined with losses in correlation with SERPs; rather, the neural network is learning to distinguish between backlink profiles far more effectively, separating the wheat from the chaff.
Domainer networks: -97%
If you spend any time looking at dropped domains, you have probably come upon a domainer network where there are a series of sites enumerated and all linking to one another. For example, the first site might be sbt001.com, then sbt002.com, and so on and so forth for thousands of domains. While it’s obvious for humans to look at this and see a pattern, Domain Authority needed to learn that these techniques do not correlate with rankings. The new Domain Authority does just that, dropping the domainer networks we analyzed on average by 97%.
Low-quality auction domains: -98%
Finally, the worst offenders — low-quality auction domains — dropped 98% on average. Domain Authority just can’t be fooled in the way it has in the past. You have to acquire good links in the right proportions (in accordance with a natural model and sites that already rank) if you wish to have a strong Domain Authority score.
What does this mean?
For most webmasters, this means very little. Your Domain Authority might drop a little bit, but so will your competitors’. For search engine optimizers, especially consultants and agencies, it means quite a bit. The inventories of known link sellers will probably diminish dramatically overnight. High DA links will become far more rare. The same is true of those trying to construct private blog networks (PBNs). Of course, Domain Authority doesn’t cause rankings so it won’t impact your current rank, but it should give consultants and agencies a much smarter metric for assessing quality.
What are the best use cases for DA?
- Compare changes in your Domain Authority with your competitors. If you drop significantly more, or increase significantly more, it could indicate that there are important differences in your link profile.
- Compare changes in your Domain Authority over time. The new Domain Authority will update historically as well, so you can track your DA. If your DA is decreasing over time, especially relative to your competitors, you probably need to get started on outreach.
- Assess link quality when looking to acquire dropped or auction domains. Those looking to acquire dropped or auction domains now have a much more powerful tool in their hands for assessing quality. Of course, DA should not be the primary metric for assessing the quality of a link or a domain, but it certainly should be in every webmaster’s toolkit.
What should we expect going forward?
We aren’t going to rest. An important philosophical shift has taken place at Moz with regards to Domain Authority. In the past, we believed it was best to keep Domain Authority static, rarely updating the model, in order to give users an apples-to-apples comparison. Over time, though, this meant that Domain Authority would become less relevant. Given the rapidity with which Google updates its results and algorithms, the new Domain Authority will be far more agile as we give it new features, retrain it more frequently, and respond to algorithmic changes from Google. We hope you like it.
Be sure to join us on Thursday, March 14th at 10am PT at our upcoming webinar discussing strategies & use cases for the new Domain Authority:
First off a little disclosure this article over laps the Backlinks category of the FAQ.
What Are Backlinks?
Backlinks are links from other sites. Think of them as votes of affirmation. Only one vote can come from a domain so for SEO purposes it doesn’t matter if there are 100 or 1 link from the same domain one link is the count you gain. Subdomains are viewed separately…thats why yourblog.tumblr.com isn’t a tumblr backlink. Now those other links may increase traffic to your site but in regards to SEO value its one vote. Some call this metric “Domain Pop” … how many different domains link to a site. It’s also gotten more complicated as people would host multiple sites on a shared IP. How many backlinks come from different IPs is “IP Pop.” It’s common to see a little higher domain pop than ip pop but if its a huge gap its suspect.
The more domains that link to you the more authoritative you must be right? Well Kinda. If 1000 domains link to your site you likely are more authoritative than a site that 3 sites link too. Not all domains or votes or backlinks….are the same. A link to your site from UltimateSEO.org carries with it the weigh attributed to that site by its backlinks. People refer to this as “link juice” basically the backlinks coming in to a site fuel the backlinks leaving a site.
Link juice prevents someone of registering 10 new domains and making 10 backlinks to their original site because those ten new sites probably lack link juice from their own backlinks. Generally said though backlinks increase a site’s domain athority or citation flow. Different companies refer to the authority of a site differently. Beyond DA and CF there is also LIS but I have found DA to be the best singular indicator of a sites worth.
You can see a site’s backlinks from many indexes, most are paid. Ultimate SEO recommends Monitor Backlinks if you want a tool that is really good at backlinks. UltimateSEO received nothing for that endorsement. The endorsement or vote …. as you see it’s a backlink.
What Kinds Of Backlinks Are There?
Beyond saying Good and Bad there are actually a couple to be aware of “follow” or “do-follow” and “nofollow.” They get their names by the instruction they give search engine crawlers…no follow links mean don’t follow this to that site. In theory a regular link is a follow link and serves as the backlink you ultimately want.
Some reason folks went a little crazy and no-followed everything … even internal links. No-follows were meant to combat link building schemes such as blog comments. While its fine to have no follow links to your site there should be a limited mixture of them in relation to your actual do-follow links. No-follow links are still indexed and I feel strongly have some SEO value still even if its just to drive traffic to your site. In the end you want do-follow links because they come as full fledged votes for your site, where as no-follows are more or less saying “here is this link to a sight I don’t want to be associated with necessarily.”
It’s that distance that makes “no-follows” a poor source of SEO efforts and its why you should use them sparingly in internal links. Why would you send a signal to Google that you don’t stand behind an internal link to yourself? Some try to hold onto all the link juice coming in and no-follow” every external link, this is a poor practice and its been shown that linking your content to relevant good external content helps you.
No-Follow Internal Links…Just Don’t
I rarely use no-follow links, I kinda think they system there is broken so I just follow them all. Sometime ago people started no-following everything and lead their link juice to specific pages they wanted to rank. Since this was a misuse of the no-follow Google changed how it handled no-follows, it doesn’t keep the juice in your site or on a page it just disappears. No-follows take the same amount of link juice as a regular link but no one gets it. Pointless then right? We’ll debate that more another day.
What Is Anchor Text?
Anchor text is the “keyword” of a backlink. Ultimate SEO for example is anchor text for the link https://ultimateseo.org which that link had no anchor text. Anchor text defines the backlink vote. If enough people make a link to your site like “Miserable Failure” it will teach Google that the target of that link is a miserable failure. This happen to George W Bush’s White House biography page long ago and is called a “Google Bomb”. It’s that old saying…if you say something often enough it can become true.
How Many Do I Need?
A lot. You need as many as you can get from as many places as you can get them. Just keep in mind that a backlink from my personal site isn’t as powerful as a backlink from the CDC.gov website …. they have the authority. Thats also why .edu and .gov backlinks are especially coveted.
A quick rule of thumb to determine how many you need is to simply Google the keyword you are attempting to rank for….lets say “cool music from the 60s.” I get pastemagazine.com leading the pack. According the SEMrush.com that site has 2.7 million backlinks coming from 36,700 domains on 44,300 IP addresses. So roughly keep that your target if you want to rank #1 for “cool music from the 60s.”
How Do I Get Backlinks?
Many ways….the Gods honest truth is to do it the obvious way …. by having content worth linking too. If you want a page to rank at the top you need a site thats fast, optimized on page, has relevant … awesome content … and people will backlink to you. Over years and years and years and you’ll need to keep that content better than everyone else’s … thats not super realistic though. Sometimes the best content is on page 2 and it’ll stay there…I often Google something and skip the first things just cause they are often just the most SEOed things. BUT most people by far pick the first result, then the second and so on.
What Are Some Popular Link Building Techniques?
So you need to prime the pump and simulate organic growth and popularity and now you’re in a link building scheme. Some are looked down upon more than others but make no mistake any attempt to gain backlinks is a link building scheme. Press Releases, Guest Blogging, Commenting in Forums, making profiles on other sites, link swapping, selling or buying links and finally PBNs. PBNs are private blog networks where you make zombie sites that link to your important site … but considering that the example above had 37,000 domains linking to it how effective is a network of say 200 sites? Well surprisingly effective…and thats why Google hunts PBNs like Buffy the vampire slayer.
Thats our Backlinks 101…I’ll talk more about some of these concepts in future posts.
So I feel like its everyone’s dream to be a media conglomerate, why buy one newspaper when you can buy 100s? Well, SEO and the internet are one big community…so in the analogy … why build multiple newspapers in the same city? No one would do that and it’s about the same with the internet or at least it should be…but everyone wants to have multiple top ranking domains.
Real Life Examples Of Multiple Domains
There is only two ways this could work out…
- Your brand is merging with another equally powerful and recognized brand and dissolving either brand will leave a huge gap that competitors will fill fast than you can with your one brand. Example … Zillow bought Trulia for 3.5 billion they represent the number one and number two home listings sites. They have continued to operate two sites in the same niche because anything other than what they have now is less than optimal. SO … you can do the same when your billion dollar company buys out your #2 competition for 4 billion or so dollars. Until then…this first scenario doesn’t work for you.
- Your brand is buying a vertical business…(word for it escapes just now but its not the point so moving on) Let’s say you make eyeglasses, you make almost all of the eyeglasses. So you buy the stores that sell them and then you buy the vision insurance company too. Thats what I mean…Your original business was production and you dealt with retail outlets, you couldn’t make hardly any more glasses so you expanded vertically in the supply chain. Its the story of that famous eye glass company you know that owns all the others… Luxottica. Never heard of them well…they did a “Multi-Domain” strategy and you have heard of these companies… EyeMed, Target Optical, Pearle Vision, Lens-crafters, Sunglass Hut, Glasses.com … theres more but you get the point. A consumer believe they have choice in the market but thats because you let them. Combined all these companies are 1/4 of all eyewear value in all the little pieces of that industry. They command it. Your new domain JimmysBestTshirtsThatRFunny.info is not them you need one domain…so buying 8 other T-shirt domains wont help you other than maybe you got a better name than that monster. Now the key part of this strategy though is vertical integration…your retail store isn’t competing with your vision insurance company and its not competing with the factory … they’re all buyers of each other till a consumer gets it.
Increased Competition But Not Sales
Thats really about it. You’re likely going to have room to grow in the sector you are in for sometime and you wont have the funds to buy up a fourth of the world’s T-shirt makers so focus on your one domain. Why? Well…changing the names to protect the guilty. I had a client who insisted on multiple domains we’ll say they were a tour company that ran guided tours of Liberty Island in NYC. Its a weird niche just cause you don’t have to have a guided tour to see the Island but because of the demand and popularity several companies sprout up and sale tickets to a national park property. Its easy money with online sales being where its at … but if you have 5 competitors sites you figure well lets add two more so now there are 7 sites and your competition adds 2 sites thats 15 now plus your 3 …. so we now have 18 sites all competing for the same audience and the same experience. Did you know that it’s really hard to rank up to the top 3 spots with one site? So now to benefit from what you’ve done you need to rank up 3 times that and fight off 15 instead of 5 other sites. We didn’t even have a second page until now in search results and someone has to be on it.
When Multiple Domains Don’t Work
So thing about your multiple domains, assign keywords to one … then move to the next domain … don’t assign the same keywords and the same role to that site, you’re just competing with yourself. Also you’re diluting your search traffic maybe combined you have 30% of the traffic but Google doesn’t see that, it sees 15% here and 10% at this second domain and only 5% at the last site. Say a competitor has a site thats at 16% his one site will out rank your three because you’ve split up all your efforts and resources. Thats the problem with the Multi Domain Strategy.
When Might You Use Multiple Domains?
I like to think I don’t do that. I have UltimateSEO.org and its SEO. I have CLoud502.com and it is cloud computing and I have data502.com and its Data Analysis. Related? Of course but very different. A person googling “AWS servers” isn’t going to click on a site about SEO. You find niches for the domains and target the audience and keywords for those domains.
So in the end, before you grow to more than one domain ask yourself if this new domain will have a different audience than the first. If not and if you can argue the same keywords fit both sites, you need one site.
So don’t eat yourself up with Multiple Domains. I’ll be posting in the next day about my addition of UltimateSEO.net .. how I intend NOT to canabalize this site.