Let's do some maths
Google page rank – Something that still stands as a golden rule to rate website’s popularity. Since the time when blogs became very popular, this metric also became crazily popular. Another one is Alexa traffic rank, which plays a good role in deciding the advertising income of a blog.
Even though it is true to some extent that Google’s pagerank does not rate the quality of a site, we must pay attention to this numbering by the big G. In this post I will explain the Google ranking algorithm behind the calculation of Google page rank.
If you are a blogger, you would most probably be well aware of what Google page rank is. But few of us know how it is calculated and the basic structure that supports it. Here is a little explanation with example illustrating the algorithm -
The original page rank algorithm has been described by Lawrence Page and Sergey Brin in several publications many times. The following equation represents the algorithm -
PR(A) = (1-d) + d (PR(T1)/C(T1) + … + PR(Tn)/C(Tn))
where PR(A) represents the pagerank of page A,
PR(Ti) is the pagerank of pages T- which link to page A,
C(Ti) is the number of outbound links links on page Ti and
d is a damping factor (a value usually selected as 0.85)
Just by having a look at the equation it can be understood that the rank of page A depends on the number of inbound links coming to it, the rank of the pages directing towards the page and the number of outbound links on the source page (the page containing the outbound link towards page A).
It can be noticed that the page rank of any page is equally distributed among all the outbound links that it contains. This means that if a page has pagerank 5 and it has 10 outbound links, then the landing pages pointed by those 10 outbound links will all have a PR5 link pointed to it.
On the other hand, the inbound links pointing to a website are weighted according to the pagerank of the page where the link comes from. The weighted sum of all the incoming links divided by the number of outbound links is multiplied by a damping factor in the formula whose value is always kept between 0 and 1.
According to one of the papers of Lawrence and Sergey the damping factor is chosen to be 0.85.
Why 0.85?
The logic behind the algorithm and the explanation of the damping factor is based on the random surfer model. Let’s say that you are surfing through internet and randomly reach a page.
If that page consists 5 outbound links on it, the probability of you clicking any one link out of those 5 will be equal; that is why the page rank is divided by the number of outbound links on it.
Now, you can reach page A in any of the following two ways
1) by clicking through an outbound link on another webpage or
2) by randomly or coincidentally reaching page A.
The probability of reaching a website by clicking on an outbound link is the sum of the individual probabilities of you clicking on those links which is the latter part of the equation. There is also a chance that after a while you would get tired and stop clicking on links and instead go for any other site through some other means.
This probability is represented by the damping factor and is denoted by d”. The entire latter part of the equation is multiplied by d to adjust for this phenomenon. A value ’1′ for d means that the surfer will never get tired of clicking on the outbound links and would never end up reaching a page which does not have any outbound link.
Now, if the probability of continuing the clicks on outbound links is d, the probability of getting tired of it or no finding a link at all and thus moving on and reaching a page randomly will be 1-d; this is the first part of the right side of the equation and the sum of both the parts represents the total probability of reaching any page.
Ahhh, is it all confusing maths? Well for me too. But it is good to know about this nah? Now let me know what you have got to say on this.
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Article by JaneSheeba
+Jane is the founder of Problogging Success. She is an expert blogger, consultant, freelance writer and blog designer. Don't forget to get your hands on two FREE Ebooks she offers.
Jane has written 262 awesome posts for Problogging Success.
{ 28 comments… read them below or add one }
I am just carious whether this old PR calculating is still applied for the latest Google Panda algorithm update.
Dana recently posted..Apple iPad 2 is in Japan and Also Popular
I am sure Panda has its own factors introduced into it. And I am so sure that it will be a secret at least for a while
Confusing but math does it all. The fact I learned from the equation is that only backlinks and outbound links matter in PR. I think it’s not a good way to give a page some reputation. Traffic and page content should be also measured.
Sumon recently posted..WordPress 312 Released! Update now
Yes, sadly only the traffic and the number of incoming and outgoing links are considered. How about quality? that is a good question.
But Google uses the fact that more links point to a blog if it has good content
Well over my head, but I’ll save this as a resource (I just subscribed).
Thanks for the reply comment at DiTescos, it meant a lot and brought me here.
Dennis Edell recently posted..Link Building and List Building – A Blog or Newsletter
Hey Deenis,
Good to see you here. Thanks for subscribing. Hope you will enjoy the stay.
Cheers,
Jane.
Jane Sheeba recently posted..Effective Blog Commenting to build high quality backlinks
Google has also announced that they are weighing links based on their prominence. So improving on the simple idea that every link on the page is the same to giving more weight to links based on placement, font style…
John recently posted..Malaysian Residence Pass for Skilled Professionals
Hey John,
I have heard about the importance of placement of links. But about fonts.. hmm I am not so sure.
Jane.
Jane Sheeba recently posted..Effective Blog Commenting to build high quality backlinks
Thanks from my side as I recalled this after a long time.
Long back, I read about it when I was in academics…Useful anyways.
One thing I am not understood that….
the outbound links plays a major role in getting a good page rank.
Then what about the links which we put in our blog to outsiders?
Don’t we get anything out of them?
San recently posted..Focus on different Java technologies FAQs
Hi San,
The outgoing links in your blog technically leaks page rank if you leave them to be do-follow. So it is a good practice to no-follow external links. But it is not always good to make all outgoing links no-follow, you might want to show some link love.
So your outgoing do-follow links do drain your page rank, but is still a good practice if used correctly.
Cheers,
Jane.
Jane Sheeba recently posted..SEO For Targeted Traffic In And Out Of Your Blog
Interesting read, thanks for breaking down this Google algorithm! I wonder if they’re ever going to review PageRanks again though… I’ve been at PR0 forever!
Cheers
Sietse recently posted..Top 8 PC Speed Up Secrets
Hi,
Have you been working on building links and SEO? If so, your page rank will increase soon.
Jane.
Jane Sheeba recently posted..Effective Blog Commenting to build high quality backlinks
Hi Jane,
Thanks for your reaction.
I certainly have been linkbuilding over the passed couple of months and I AM seeing good results. However: Google’s PageRank hasn’t been updated in well over a year and although I myself don’t believe in numbers like PageRank, websites are still rated on it.
For example: getting a proper advertising deal usually is based not only on your alexa rank and all the statistics it brings, but also on your Google PageRank. If Google decides never to update it again, I will just be stuck at PR0, even though I currently get about 1,000 unique daily visitors through Google search queries.
Sietse recently posted..Eating Well- The 5 Best Foods for Your Teeth
Actually it was updated for the first time a short time ago, not everyone noticed. Whether they continue or not is everyone’s guess.
Dennis Edell recently posted..Link Building and List Building – A Blog or Newsletter
This post is really superb, people who do blogging read this! Thank you very much for sharing this information with us, as I am looking for a higher PR and ways how to achieve it, this really will help.
Lawrence recently posted..Identity Theft Statistics and What to Do
Hey Lawrence,
I am sure that a knowledge about Google PR is a must for every blogger. I am glad that you liked the information.
Cheers,
Jane.
Jane Sheeba recently posted..How to build a better blog Do it now- really
Do you fear that you will somehow lose your Google PageRank by doing this? Whenever I read articles on and other publishing sites that operate in the same manner I am amazed that people writing articles miss out on the most obvious links they could include in their articles to make them more interesting to make following up on a theme more easy for the reader which I consider common courtesy toward the reader who wants to know more and to improve your Google Page Rank. The arguments run along two lines on one hand that outbound links drain your by somehow metaphysically jumping to other pages I suppose and on the other hand that the massive reciprocity of all those sites you linked to will result in enough inbound links to cause Google to think youre using magical black hat techniques..Neither of these arguments holds water..First outbound links do not somehow inexplicably cancel out the good that inbound links do to your articles.
Nice Article. Google is Best .
Akash recently posted..Download Android Pizza Hut Application
The first half part of the post and the last part totally contradicts what the post claims . First you claim that PR is equally distributed to all outbound links then you go on to explain the Random surfer model in the conclusion !
The RSM was built for the sole purpose of differentiating the value of link juice passed to all links and it is never same for all links ….
Fell short of analytics and research while writing the post maybe ?
Also the algorithm was never a secret , its freely available on various SEO blogs and the formula has been there on wikipedia , infact with the very same variables …..
As for your claims on panda update , it was a corrective measure for the 2009 Google caffeine update which is related to SERPs and not PR and FYI the PR algorithm is not owned by google but patented to Stanford university where it was built initially as a college research project by Larry Page .. the patent expires in the year 2011 , which is the same year you discovered the ‘secret’ .
Nice post …
Rohan recently posted..Common Computer Issues & How To Solve Them
Hey Rohit,
If you read the post very carefully, you will understand that I am not writing that I have “discovered” the secret. I am sharing my thoughts on the algorithm at my blog and I am sure that I can do it. It is not a copyrighted material and yes I know that the algorithm is there at Wikipedia with the same variables; that is not my point.
And the word “equally” on outbound links does not represent the weight here.
Thanks for your comment.
Jane.
Jane Sheeba recently posted..Top 5 ways of building effective backlinks for your blog
This is the post which i am looking from many days.
Thank your very much for sharing Google page ranking algorithm
Sanjan Bikram recently posted..Add website to Yahoo and Bing Webmaster Tools
This post of google pagerank is one of the best post I have read till now in seo world
Torry recently posted..RIL AGM 2011: Reliance Industries conceptualising products, services for mobile broad
Lol, i’ll have to come and finish this some other time, i got a headache around the middle of the article. But like you said, it’s good to know how things are done and that they’re not random, like some thought.
Martin recently posted..CDL Classes – How to Become a Professional Truck Driver
In my opinion, today algorithm google have more complex algorithm than above formula in calculating page rank. i have a blog with log of incoming link but the PR still zero
.
BR//
syakur recently posted..Mengetahui Gejala Hernia
While the algorithim you present is a little difficult for me to absorb, I am sure the actual one in use goes far beyond this in complexity. Surely some weight is given to content and other factors.
Jeff recently posted..New Rice Cooker Recipes Added
This is something that I could not understand even if I spend much of time for it.
adam recently posted..Tagalog Love Quotes Collection
Google PageRank is important for every site. No of links coming to your site are important for getting good PageRank.
Rajesh Namase recently posted..Search Engine Optimization Tips for Blogger
This is great article, I learned many good things here but I have just one query, My web site is hosting related so which blogs category should be best for commenting? My friend said that hosting related blogs will not give you backlink, please suggest me.
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