I think PageRank (PR) was discussed, debated, argued since the day Google emerged and that is not surprising, Google based (and still does?!) its search results heavily on that factor.
What is PR?
PR is a number calculated in a very simple way, its a 1-10 normalized sum of all the “backlink power” a specific page received. How does a “backlink power” calculated? Take the power of the page giving the link, divide it by the sum of the links it gives (and multiply it by some factor, it is an unknown factor, but people like to give it the value of 0.85).
For example, if a specific page has a PR5 and giving backlinks to 10 sites then the “backlink power” should be 5/10*0.85. But it is not accurate since the PR5 is a sormalized number, which means a PR5 actual value can be anything, but lets say its 1000. So here is how much “backlink power” a specific page will receive (with the above assumption):
So if I get a link from a PR5 page that is linking to 10 pages, I will get 85 points. Lets continue with that line of thinking. If the real value of a PR5 is 1000, lets say my page is a PR4 with 900 real value, now it will become 985, I will see no change of my PR although I got really closer to become a PR5.
How come PR1 page can rank higher than PR10 page?
PR is a factor that won’t help you at all if its not a part of the bigger picture. Its like asking how come my car won’t drive fast if its having a Mercedes engine, does it have good wheels? Gear? Fuel?
A PR will answer the question “how strong is that page?” but this question and answer is quite stupid without the missing part: “how strong is that page in that subject”.
A high PR reminds me a very respected person, like a well known scientist, if you’ll meet a noble prized scientist will you ask him about physics? medicine? chemistry? You won’t know what to ask him about if you don’t know whats his specialty. Same with PR, high PR page is nothing without understanding whats its specialty.
But things are getting a bit more complex than that. Lets say you meet a physics scientist and ask him a question in chemistry, how much would you value his answer compared to a regular guy/a begger/BA student in chemistry answer?
We would always want to receive backlinks from PR10 sites which are about our niche, but we all know that its not so simple. So, what would we prefer a link from a PR4 page that is more or less about our subject or a link from a PR1 page that is exactly about our subject or a link from a PR7 page that talks about something else altogether?
No one but Google can give you a good answer to that question and usually a common sense would guide you finding whats the right call (well, I usually believe that I’d accept links from any legitimate source, but what we should do when we have to choose?).
Here is a simplified formula I’d use. First we need to estimate the pure value of a link. Lets break down PR. It is popular to consider ever PR jump value in multiply of 6, which means if PR0=Y then:
PR1 = 6*y
Which means when all other factors are the same one link from a PR4 page equals 1296 links from PR0 page!
But, all factors are not kept equal, let run an example:
I’m offered a link from a PR5 page with 19 outgoing links already there (20 with mine) or a link from a PR3 page with only my link in it.
My value from the PR3 would be: 216 times a link from PR0 value.
My value from the PR5 would be 7776/20 = 338
So I’d prefer the PR5 link with 20 outgoing links in it, but is a link from a PR4 page with 3 out going links is better?
1296/(3 – the outgoing links)=432 the value of a Pr0 page, which means I’d prefer that link over the PR5 link!
You probably noticed I didn’t take the 0.85 factor into account, since it is equal in all comparisons there is no need to use it here.
Lets make things a bit more complicated…
I have been talking about that PR has no significance without understanding the subject the page is about, so how can I compare PR4 to PR5 when I don’t know about what each page is?
Here is my suggestion, since Google algo is based lots on semantic nets , the further the sites subject is from your subject the weaker is the link, computing the length should be based on semantic relation. Example: The length between dog and dog is zero, the length between a dog and a pet is one. The length between a pet and cat is one, hence the length between a dog and a cat is 2.
Again, it is a very simplified example, I use it by calculating the distance between my subject and the page I can get a link from: My page: seo, link offered from : php info site, distance:
seo->internet->websites->php, it could also be:
seo->websites->php, in that case where I think about several reasonable options I take the average of them all, 2.5 in that case.
Ok, now I like to multiply it by a factor (I use 5), so we have 12.5 and the real SEO value Im going to get from a PR5 page about php with 20 outgoing links to my SEO page is:
My value from the PR5 would be 7776/20 = 338
What do I do with that number? I compare it to the alternative and decide where I get the highest SEO value, there I try to put my links!