PageRank

SEO: Illuminating the value of URL design

If you’ve read many of our other posts here at The Well Designed URLs Initiative, you know that we are strong advocates for User-Centered URL Design as well as for URL Literacy. It’s our contention that the URL is woefully under-appreciated as the most fundamentally important technology of the web, more important than HTTP, and even more important than HTML. The purpose of this post is to provide background for future posts explaining URL design importance from a perspective most website owners can appreciate; search engine rankings!

But they’d have to kill you

For those unfamiliar with Google’s core algorithm for determining its search engine results, you can read this article to learn about PageRank in more painstaking detail. Here, I’ll just try to explaining the aspects of PageRank as it relates to URLs. Note also that my explanations are simply meant to be a conceptual guide and not exacting details. The founders of Google did publish their initial algorithms but have since made tweaks that are as closely held a corporate secret as the formula for Classic Coke!

Popularity is the key

PageRank ias essentially a popularity rating, and a page’s PageRank is determined by the inbound links from other pages on the web. A PageRank can be as low of almost zero (0) to as high as ten (10). Google’s algorithms determine a page’s PageRank by dividing the PageRank for each of the inbound linking pages by the number of outbound links on each of those pages, factoring in each page’s PageRank, and then summing the results for all inbound links. Clear as mud, right? It’s easier to explain with an example, but let’s cover a bit more ground first.

Like voting company shares

PageRank considers each link a ‘vote’ for the page linked to. But unlike in a democratic “one citizen, one vote” society, Google’s algorithm more closely models the shareholders of a corporation voting their shares; the votes of those with “more” (PageRank or shares) have a greater influence on the outcome. So a link from a page with a PageRank of 7 is more valuable than a link from a page of PageRank 3; probably many orders of magnitude more valuable, as you’ll see next.

The old 80/20 rule, on steroids

Because of the nature of the web, a small number of pages have a huge number of inbound links, and vice versa. So those with more links get more PageRank, but the value of PageRank is on a logarithmic scale thus it increases exponentially. Assuming[1] that the base were five (5), the value a page would get to vote based on it’s PageRank would look like this:

PageRank Value
0 0
1 5
2 25
3 125
4 625
5 3,125
6 15,625
7 78,125
8 390,625
9 1,953,125
10 9,765,625

An example:

Assume a site somehow manages to get a persistent link from MySpace’s home page (www.myspace.com). At the moment contains MySpace’s home page contains about 70 outbound links and has a PageRank of seven (7). Let’s also assume that there are a total of 50 other inbound links, and let’s say the average PageRank for those pages linking in is three (3) and those pages have an average outbound link count of 10. From this, let’s calculate PageRank:

MySpace’s Available PageRank per outbound link:
78,125 / 70 => 1,116
PageRank value contributed by 50 other sites:
125 * 50 / 10 => 625
Total PageRank value:
1,116 + 625 => 1,741

Looking it up in the table, the resultant PageRank for the home page is four (4).

The Three ‘P’s of Inbound Links

As with the three ‘L’s of real estate, the three ‘P’s of inbound links are: PageRank, PageRank, PageRank! [2] Note how in the prior example the 50 inbound links of PR3 offered less PageRank than the one (1) inbound link from MySpace with PR7! Of course we don’t know the logarithmic base [1] but Phil Craven says 5 or 6 are what many people believe it to be.

Here is what it would look like with base two (2) through ten (10) (download the full calculations here as a zipped Excel 2003 file [4kb]):

Logarithmic
Base
Value from
PR3 * 50 / 10
Value From
PR7 * 1 / 70
Total
Value
Resultant
PageRank
2 40 2 42 5
3 135 31 166 4
4 320 234 554 4
5 625 1,116 1741 4
6 1,080 3,999 5,079 4
7 1,715 11,765 13,480 4
8 2,560 29,959 32,519 4
9 3,645 68,328 71,973 5
10 5,000 142,857 147,867 5

So depending on the logarithmic base, PageRank fluctuates between four (4) and five (5) for this hypothetical example. However, starting with a logarithmic base of five (5) the one MySpace link overpowers the 50 others! And because pages with a PageRank closer to 10 are listed higher in Google’s search engine results page among competing pages, people focused on SEO are always trying to increase their page’s PageRank, often via unscrupulous means.

Of course nobody outside Google knows the exact formula or base exponents used, but hopefully this post illustrates the value of links from high PageRank pages.

Don’t game the system

However, I would be remiss if I didn’t point out that a single-minded focus on inbound links is fraught with peril, not the least because it might cause your pages to removed from Google’s index! Just as there are people selling weight loss products they claimn don’t require dieting or exercise, there are people offering ways to inbound links that don’t require having real people link to you. However, Google considers these shortcuts to be gaming the system is ever vigilant to discover those cheaters. If caught cheating, Google will ban your pages from their index without notice.

The best way to gain inbound links for your key pages on your website is to do the hard work of creating a site with great content that people want to link to.

Architecture Matters

So as an epilogue, getting inbound links is clearly necessary for high PageRank and thus good search engine results, but all those inbound links can be squandered without a good architecture and site management plan. To ensure that a site’s great content and popularity get reflected in appropriately high search engine ranking it’s critical to optimize the architecture of the site, the pages, and the URL structure as well as make plans for how the URL structure might change over time.

The most under-realized aspect of SEO

Personally, I think the most under-realized aspect of white hat SEO [3] is the lack of attention paid to URL planning and design, especially for larger websites. There are very few tools [4] besides the low-level and effectively simplistic URL rewriters like mod_rewrite for creating and maintaining a URL plan, very few articles [4] that discuss URL design, and no articles [4] I am aware of that discuss URL planning.

However, I believe website owners will see huge improvements compared to their prior rankings if they focus on URL design and create a URL management plan. The good news is that URL design is mostly a one time endeavor assuming site maintainers adhere to the management plan, at least until there is a full site rearchitecture.

But all of the whys and wherefores regarding URL planning and design are beyond the scope of this post, and instead will be the subject of many posts in the future. Stay subscribed!

For Further Research

And, as I stated at the start of this post you can learn more the PageRank formula here, and you can also google for PageRank to get a large list of other resources.

Footnotes

  1. But remember it’s a secret, so we can’t know for sure.
  2. There’s more to search engine ranking than just PageRank, like applicable content, but PageRank differentiates pages that compete competitive for the same keywords.
  3. To those SEO-haters of the world, please note that I’m referring to those things that you can do with pure white hat techniques, things that if not done can result in a great site being given less credit by the search engines.
  4. Over time, I plan to address the lack of such articles and tools for URL planning and design.

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8 Responses to PageRank

  1. Pingback: Cape Cod SEO - Maintaining the Sex Appeal of Your Web Addresses

  2. How much weight do you think google currently puts towards the anchor text to a link now? Do you think it holds some mulliplier to overall PR value?

  3. @beevers99: I wish I knew. I think it is still pretty important, but you’d have to ask others who follow it more closely than I to get a better answer.

  4. The URL http://blog.welldesignedurls.org/url-literacy/, which I’m certain was incredibly well designed, is currently a 404. Maybe it always was, and linking it from this blog post was a mistake of some sort. Either way, I’d love to understand what went wrong with this URL and how it fits into the philosophy you advance on your site.

  5. @Jay Freeman: Doh! You caught me and have got a great point. Frankly if memory serves it was a typo that I meant to go to the wiki not to the blog. And yes, I create links to the wiki that I don’t always fill out later, but the URLs are still well designed. :)

    I’ll fix it up.

  6. Very nice thread,

    Looks like it takes whole life to get PR7. I will not even talk about PR8+

    The thing is even if you know the scale of PR is calculated – you can try fool arounf the SE’s, but one day they will find you – and you will be done!

    So as I believe, the best way is the longest way, it is much safer and better to grow gradually, than the next update get the “desired” PR and after that in the following update enjoy no traffic at all….

    Best of luck!

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  8. Phill says:

    A very old post, but very very good read! I love your theory here, particularly the 3 P’s of page rank.

    cheers

    Phil

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