With these reference points in mind, we have created two new concepts; The Domain Authority Index and The Link Authority Distribution Index, to model the cause, effect and relationship of both metrics on search rankings.

We propose that Linking Domain Authority and on-site Domain Authority are directly related to each other, with on-site scoring governed by the authority of linking sites.

However, volumes of high authority links do not necessarily result in higher on-site authority.  Acquiring a high Domain Authority score shares a stronger relationship with an evenly distributed authoritative link profile rather than quantity of links. 

The Domain Authority Index

The Domain Authority Index examines on-site Domain Authority, Average Linking Domain Authority and Total unique links.

The analysis involves six months’ worth of backlink data from the top 35 ranking URLs for 650 volume keywords. This equates to approximately 9,500 URLs and aggregates the data for 950,000 backlinks.

The index highlights a potential irrelevance of Linking Domain Authority when paired with a large volume of unique links to a site.

It demonstrates that on average a count of 26 or more unique links to a site will render those from higher ranges obsolete and such links could actually have a negative effect on on-site Domain Authority. 

This insight offers brands a valuable concept in that there appears to be a ‘sweet spot’ in terms of link acquisition: acquiring high volumes of any one range of authoritative links may not provide optimal ROI in terms of Domain Authority enhancement and positive movement in rankings.


Figure 1: The Domain Authority Index; the areas highlighted in red denote danger zones where sites with similar metric values are likely to be declared artificial or unhealthy.

Figure 2: Examples of varying URL make-up, marked on the index in Figure 1. Eastcoast.co.uk demonstrate a healthy backlink profile whereas Amazon are only just out of the red zone due to the sheer volume of links pointing to their domain

Our analysis provides a view of the current link building landscape though it doesn’t take into account link type, placement or source. The introduction of social leaves sites indebted to multiple platforms with little option but to incorporate a social element into their blended search strategy.

Social links need to be considered in addition to traditional link building activity as does the weight and potential volume of links provided through social platforms.  

The Domain Authority index offers a degree of clarity towards where brands should be aspiring to work to in terms of their ‘link mix’ by highlighting which sites could potentially be categorised as ‘artificial’ or ‘healthy’ by Google, thus reducing the risk of penalties and ranking volatility.

The Link Authority Distribution Index 

The Link Authority Distribution Index shows the average distribution of links over authority ranges as percentages. The dataset includes 100 top ranking sites across key sectors and link data from 95,000 URL’s. 

The index illustrates the relationship between Linking Domain Authority and on-site Domain Authority and concludes average Linking Domain Authority distributions.

Figure 2: The Link Authority Distribution Index

The Link Authority Distribution Index clearly shows that authoritative URLs possess links of varying quality including those from the lower end of the scale. This supports our previous suggestion that a healthy back link profile will have a greater degree of variation in authority of linking domains.  

Interestingly, the Link Authority Index illustrates a direct relationship between actual on-site authority and the highest proportion of backlinks to the destination site.

Looking at sites with an average Domain Authority score of 11–20, you can see that the majority of links to those sites (50%) are from the matching range. This pattern is simulated across all Domain Authority ranges.

Whilst not a definitive indication of how on-site Domain Authority is calculated, from this analysis we can begin to speculate what an ideal backlink profile looks like, without the requirement to analyse the entire make-up, and draw comparisons between link building strategies within different marketplaces.

Interestingly, the greatest proportion of high authority links (highlighted in the darker blue in the table) decreases exponentially as the Domain Authority range increases.

This indicates the difficulty of both acquiring high authority links and the inherent challenge behind acquiring high on-site authority. When examining the lower end of the authority spectrum, the converse is visible, illustrating ease of acquiring lower quality links.

It’s easy to see from this analysis the overhang from rapid, volume based, link building strategies of the past and the inherent difficulties in reversing this approach for link building across the authority range.

This also begs the question, should brands be interested in building quality, authoritative links when the Domain Authority Index alludes to a remaining reliance on volume over value when it comes to overall on-site authority?


Examining both the Domain Authority and the Link Authority Distribution Indexes, it is clear that effective and successful link building centres on quality and quantity, and more importantly is about the correct distribution of Linking Authority across the range in order to reap the benefits of resilient ranking and to be successful in commanding an authoritative site. 

All data has been sourced from Stickyeyes’ search software, Roadmap.