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Search Engine Pagerank Explained

Understanding Search Engine Pagerank

The pagerank of a webpage is very important when determining search results within search engines, more so when the keyword or keywords for that page are very competitive. Obviously for more unique search terms there will be less competition for places and therefore the pagerank is less important. In general a good pagerank is a reliable measure of the success of a webpage and the higher the pagerank the more traffic you will get from search engines.

So let look at some numbers, Google for example allocates a value of between zero and ten to every page it encounters where one is low and ten is very very high. Zero is generally given to pages which it has not yet determined a page rank for reason for this may be that the page is new, however a zero ranking is also given to pages which are banned or deemed as spam.

At this point it should be noted that pages with a zero page rank are still valid and will often show up in Google results pages but they are unlikely to feature for competitive search terms or will appear very far down the list of results.

How Is Your Page Rank Calculated

Pagerank at a basic level is actually quite simple, if we think of it in terms of a score or points system where respective pagerank is obtained depending on the score of the page. Take a look at the table below which shows a possible relationship between pagerank and a pages score (This is purely hypothetical and is used for illustrative purposes only).

Pagerank / Score Relationship. (Hypothetical)
Pagerank Score / Points
PR 1 1
PR 2 10
PR 3 100
PR 4 1,000
PR 5 10,000
PR 6 100,000
PR 7 1,000,000
PR 8 10,000,000
PR 9 100,000,000
PR 10 1,000,000,000

Now for example take a regular homepage page A and assume it has a pagerank of 5 and therefore a score of 10,000. On this page there are 5 internal links to pages B-F. The 10,000 points of page A are then divided between each of the linked pages giving them 2,000 point each and therefore by consulting the above table a pagerank of 4.

For the mathematically minded out there this could be written as.

prA ⇔ prB + prC + prD + prE + prF

The point to understand is that pagerank is passed from one page to another throught hyperlinks which is why people often say that links from higher ranking pages are much more valuable than from lower ranking pages.

I'm sure by now your getting the idea. The above example is very basic and many other factors can influence the above equation, keep reading if you would like to know a few possible factors.

Additional Factors Affecting Pagerank

There are of course many other factors to consider when assessing the way pagerank flows around the web, they are not definite but in my opinion well worth a mention.

Decay Factors

Firstly there is almost certainly a decay factor built in, what I mean by this is that not all of a pages score will be passed on to the pages linked to from within it. No one can know for sure what the rate of decay could be but let us use 20% as an example. This would mean if we go back to the above case page A which began with 10,000 point, would lose 20% or 2,000 points before passing its pagerank on.

So our equation would now look something like this.

(1 - E) x prA ⇔ prB + prC + prD + prE + prF
Where E = decay factor

Relevance

Similarly there is likely a relevance factor lets say β which would take on a value assigned by the search engines based on their determined relevance of the linked page. Meaning that when a link is found a search engine will compare the referring page and the linked page to see how relevant the links is likely to be. The value will be a variable probably between 0 and 100%.

Think about this when exchanging links with other sites or web pages, you will get no negative effects from a poorly source webpage but you may be getting very little positive effects either.

The equation will now look something like this.

β x (1 - E) x prA ⇔ prB + prC + prD + prE + prF
Where β = Relevance factor

Authority

Recently Google has been talking alot about the authority of websites and in my opinion it is very likely that the authority of the linking website must play some part in the allocation of pagerank. Much like the relevancy variable the authority factor will most likely be a value between 0 and 100% with higher values being awarded to older more established and therefore authoritative websites.

The equation will now look something like this.

α x β x (1 - E) x prA ⇔ prB + prC + prD + prE + prF
Where α = Authority factor

There are many more factors which are likely to effect the flow of pagerank from one page to another but the above are the ones which I believe are likely to have the greatest effect. My opinion is that people often over complicate pagerank, keep the above in mind when you are looking to build links and you will have a stronger basis than most.

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