Page Rank: Can It Be Used?
One of the factors that SEOs have a made a big deal about for a while – and many still do – is Google’s Page Rank. This isn’t the most important factor in deciding the page’s ranking, and seems to be growing less important as time goes on – but because it’s been seen as a major factor in SEO for quite some time, it’s worth a discussion. Additionally, the idea behind the calculation of Page Rank is probably the basis, on a very basic level, for most calculations of any kind of “rank”.
What’s the Idea Behind Page Rank?
The more a site becomes established as an authority in a particular area, the more people will turn to the site (external inbound links). The Page Rank measurement reflects the number of incoming external links to the site and their quality. It is not at all dependent on keywords.
Page Rank is calculated according to the following formula:
PR=(1-d) + d (PR1/L1 + PR2/L2 + … + PRn/Ln)
PR is the Page Rank of the page
PRn is the Page Rank of a page that connects to the page.
Ln is the number of links that are found on that connecting page.
d is a set damping factor between 0 and 1.
The significance of the formula is: the page rank is the sum of the page ranks of all the pages that link to the page in question divided by the number of links that leave those pages. (There’s a big disclaimer to this: Google can choose to give different “PageRank passing value” to different links on a page. See “Channeling PR” further on.)
Conclusions Based on the Formula (and the Formula Alone)
· There is no difference between an external and an internal link as it contributes to a page’s PR. In fact, for a website, the more pages in the website, the higher its potential PR. This assuming that the pages link to each other in a manner that facilitates channeling of all the potential PR.
· The more links that connect to a page, the higher its PR will be.
· A page does not lose its PR when it links to another page, but there does exist a phenomenon of wasting PR. If a page links to many sites, it will have less PR to spread via internal links to the pages on its own site. Additionally, its links will not be worth that much because they will be spread so thin. The reverse is also true, worth bearing in mind when choosing which pages to try to attain links from: if a page receives a link from a page that contains many links, its link will not have a large effect on the PR of the page.
A representation of the result of this measurement can be seen for any site in Google’s toolbar (most recent update happened in January 2011). This representation is one of ten categorizations: PR1 PR10. At PR1 (the lowest ranking), many sites are found. The higher the number, the more exclusive the list of websites that receive it. It’s believed that these categorizations follow a logarithmic scale, making it much harder to go from PR7 to PR8 than from PR3 to PR4, and also exponentially increasing the value of a link from a site with a higher PR.
What happens when a number of websites link to each other?
When many sites link one to the other they cause a type of feedback system that constantly changes the ranking of all of them (after the ranking of one of the pages is established, the ranking of the second changes, and that in turn affects the ranking of the first page as shown by the formula). By means of the formula one can prove that that after a certain number of iterations, the change in the Page Rank of all the pages in the system is no longer significant.
If this topic interests you, here is a more detailed explanation of Page Rank.
Channeling PR?
You could seemingly take advantage of this formula in order to increase the PR of your website’s internal pages. This is important since Google often displays internal pages in its results, and not just the homepage. You would do this by changing the internal link structure of the site. This endeavour needs some slightly complicated calculations, but the principle is that for the pages that you want to promote, you put links on all other pages of the website, whereas for pages that you want to have less power (since giving strength to some pages within a site means taking it away from others), you only have a few links within the site. Don’t try using the nofollow attribute to achieve this goal, however – Google announced in mid-2009 that nofollowed links simply eliminate from the system the PR that would have been passed through those links; the PR is not then conserved to strengthen your followed links. Google also indicated that the percentage of overall PR passed through any link on a given page can vary at their discretion, making attempts to mathematically compute your exact PR passing ability nigh impossible. In any event, it’s worth putting the effort in to have a good internal linking structure, let Google decide the details as it will.
Give a link from the home page to the pages that you are trying to promote, since it’s almost always the strongest page on the site.
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