PageRank vs. MozRank

Please Note: LinkScape and MozRank have been updated since this publishing. The graphs and data below are no longer accurate, albeit still interesting IMHO.With the announcing and opening of the fantastic SEOMoz MozRank API for Linkscape, I thought it would be worth taking a bit of time to compare MozRank to PageRank using existing and fresh PageRank data. Essentially, we wanted to determine if there were any patterns of dispersion between the MozRank and PageRank for random pages across the internet. Using the API, we were able to collect data on 1000 various pages. We selected only pages above PR0 to discourage the likelihood of identifying pages with no MozRank data. We also, as expected, have a skew in the representation of higher PR data, as they are just not as common. *Be sure to read Nick from SEOMoz’s Comments Below

Using exiting PR data, we were able to see a clear pattern in the differences between PR and MR as PageRank increases. As PageRank increases, MozRank is more likely to under-represent the actual PageRank (PageRank minus MozRank = The Blue Dots). Once a page or site reaches a PR5, MozRank almost always under-estimates it’s value, which would be represented by a blue dot below the 0 line.

In order to make sure that our tests were not being hindered by aged PageRank data, we ran a similar test with only 100 unique URLs but grabbed the PageRank on-the-fly. As you can see in the representation to the right, a similar pattern emerged. Low PageRank pages were more likely to be over-represented in MozRank data.

The more interesting item to note is that it appears MozRank and PageRank are most similar at the PR3/MR3 range. If you see a PR3, you are likely to see between a MR2 and 4.

I ask you to take this post with a grain of salt, though. I am looking at a very small data-source with very rudimentary statistics. Perhaps someone more talented than I could do a followup. Kudos, once again, to the SEOMoz team for this great resource.

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  1. Ben Hendrickson
    Feb 10, 2009

    I’m impressed how quickly you produced this! The chart looks rather simular to some I’ve seem Nick make here at the SEOmoz office.

  2. Nick Gerner
    Feb 10, 2009

    Nice post. And good feedback. This is a familiar graph… mR as you see it is actually scaled in a somewhat arbitrary way (at the moment). You could get a better match by doing a linear transform. This won’t affect the relative comparisons between pages (the order of mozRank).

    Then again, PageRank is probably mixing up a lot of effects beyond pure link popularity (e.g. domain authority, domain age, penalties, …)

    Try adding noise (e.g. =PR+RAND()-0.5) to get a prettier graph (less bunching up due to lack of PR precision). That illustrates the correlation better 🙂

  3. Nick Gerner
    Feb 10, 2009

    oh yeah, you should join our google group if you’re interested in more SEOmoz API dev stuff:

  4. Bert
    Sep 8, 2009

    I don’t know about Mozrank. I’ve seen highly trusted domains (government sites) with high Pagerank and very low Mozrank and some commercial sites with low pagerank 4 and a very high Mozrank (even a score of 8.3, beating, yeah! ).

    So I take both measures with a huge bottle of scientific salt.

    Author Note: Google’s Toolbar PR is not an accurate measurement of the actual PageRank. It is qualified by anti-spam measures. For example, a page that sells links may have its Toolbar PR decreased but its MozRank will still remain high. However, this is rare enough that across the board we see a fairly reasonable correlation between the two.

  5. Free Domain Check
    Oct 16, 2009

    It’s always refreshing to read your posts – thanks again

  6. Horeca Jobs
    Jul 29, 2010

    Thanx for the info! Its not getting easier, is it… 🙂

  7. SEO Experts
    Aug 28, 2010

    Yeah it’s difficult to identify on what basis the mozrank is decided and how the site are rated, as it is different from the expected results!

  8. Siju George
    Apr 26, 2011

    So what do think more relevant ? If PR is not updating at its normal interval ( once in 3 or 4 months), the toolbar PR may be very wrong to make any conclusion about the website. So as a marketer can I trust Moz Rank to determine the current value of the website ?


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