Google PageRank

Posted by admin in Uncategorized on 10 16th, 2007 | View Comments

By Jenna Ryan – October 2007 – The Marketing Shop.com

This article is a compilation of theories and a work in progress.

Page Rank (PR) is Google’s way of ranking websites. It started out as a university project by Sergi Brinn and Larry Page, founders of Google. Ironically, the title “PageRank” suits both its purpose and the last name of its founder. It is the PageRank Technology that has served as the foundation of the company’s success and speed in ranking sites better than its competitors.

PageRank is only part of the formula for determining the ranking of a website. In fact, Google employees over 100 other algorithms in it’s quest to find the most relevant sites for end users. The original paper by Google founders, “Anatomy of a Large-Scale Hypertextual Web Search Engine,” is linked in the references section of this article.

For the average website visitor, PageRank can be a fun way to compare the relevancy of the different sites we encounter. The fun green graphic bar used to demonstrate PageRank is addictive, but is only an estimate of the ranking of the site, and not meant to be scientifically accurate.

Fundamentally PR is determined by the quantity and quality of incoming links to the website (Google), PageRank works because it simplifies the entire linking structure of the web (Sobek) and the billions of links and content that it contains.

PageRank has no doubt changed emmensely since Google’s humble beginnings.

Though Google keeps its ranking technology a secret, we are able to glean much of its structural elements from the paper written by Google founders at Stanford College (see references). We also have the bits of information that Google provides here and there but. Other than that, it’s up to the SEO Experts to theorize as to what PageRank is now and where it’s heading.

In essence, PageRank is determined by Link Popularity (Sobek), or votes by one site in support of another (Rogers):

Site A links to site B therefore site B must be important.

PageRank is only an estimate of Web page significance (Ridings).

Link Popularity

Link popularity is faked by webmasters who create masses of inbound links for doorway pages from just as insignificant other web pages. (Sobek)

Other Website Ranking Factors

Don’t be fooled by the title “page rank” because this system is only one way Google ranks websites and web pages. Other factors include on-page (keywords, content, meta tags), and off-site factors factors (links, anchor text and penalties).

Incoming Link Value

All incoming links are not created equally. Some links coming into a Web site have more value than others depending upon the quality of the linking Web site and Web page:

Page Rank of the outbound link page
PageRank of the links linking to the outbound link page
Number of links on the outbound link page
Quality of the outbound link page
Penalties (or not) of the outbound link page

PageRank is a vote and thus is transferred to the referring website. This means that a high ranking Web page gives PR to the receiving page.

The rank of a document is given by those documents that link to it (Sobek). Rank of a document is always determined recursively by the PR of other documents.

PR for Webmasters

Page Ranking is one of the most difficult ranking factors to control. (Ridings)

You can likely reach the top without implementing PR tactics, but a strong PR campaign can make it difficult for competitors to catch up. (Ridings)

1. Incoming Links – Which sites will you go after?

2. Outgoing Links – The page you link from to generate PR Feedback and

minimising PR leakage.

3. Internal Navigation – Distributing links among the pages in a website to spread PR for desired effect.

PR of the actual linking page is important, not the PR of the home page.

The PR of the page is shared among all the links on the page.

Weight of Page Rank on Google Rankings

The value of and actual structure of the PR algorithm can only be debated in SEO circles because Google is very secretive about the its actual configuration, and rightfully so since they invented it. Still, Google has spoken on the topic and each time confirms the validity and importance of PageRank as an ongoing concern for Web site rankings.

“Because of the scalable approach PageRank uses to analyze links, it will continue to be a significant factor in Google’s search results.

However, because it is a rough estimate, the value to search engine optimization professionals is limited.”

Exerpt from Q&A with Chirs at Google in PageRank Explained Thesis (2002)

Reciprocal Links have been devalued. (verify)

According to some SEO Experts, Page Rank has a great deal of value, (Mutch) while others say it’s important not to “over-estimate it’s usage and capabilities.” (Ridings)

No matter what the consensus, Google is constantly updating its algorithm to prevent manipulation of its rankings

There is no doubt that the weight of PR is decreasing as more webmasters figure out how to manipulate the Page Rank system, much like the decline of meta tags in earlier years. (Ridings)

Like any other ranking method used by Google that is eventually devalued, Page Rank also seems to be less important to the rankings of a page. (Ridings)

Quoting from the original Google paper, PageRank is defined like this:

We assume page A has pages T1…Tn which point to it (i.e., are citations). The parameter d is a damping factor which can be set between 0 and 1. We usually set d to 0.85. There are more details about d in the next section. Also C(A) is defined as the number of links going out of page A. The PageRank of a page A is given as follows:

PR(A) = (1-d) + d (PR(T1)/C(T1) + … + PR(Tn)/C(Tn))

Note that the PageRanks form a probability distribution over web pages, so the sum of all web pages\’ PageRanks will be one.

PageRank or PR(A) can be calculated using a simple iterative algorithm, and corresponds to the principal eigenvector of the normalized link matrix of the web.

Okay, so you didn’t sign up for a mathematics course, but in a nutshell the above paragraph shows us the following:

1. Every website has a numerical value

Website A = .50
Website B = .50

2. The sum of all the websites online = 1

A + B = 1

3. Links on a page have value that is divied among all the outgoing links on the page. The link giving site does not lose PR, but the receiving site gains PR value. The amount of PR the receiving site receives depends on the total number of outgoing links resident on the linking site’s page.

1 link = 100% Value
2 links = Each Link gets 50% value
4 links = Each Link gets 25% value

Beyond this, the calculations get very complex. There are very good articles explaining the original PageRank algorithm in the reference section at the end of this article.

Initially, the ranking of web pages by the Google search engine was determined by three factors:

Page specific factors
Anchor text of inbound links
Page Rank

Page specific factors are, besides the body text, for instance the content of the title tag or the URL of the document. It is more than likely that since the publications of Page and Brin more factors have joined the ranking methods of the Google search engine. But this shall not be of interest here. In order to provide search results, Google computes an IR score out of page specific factors and the anchor text of inbound links of a page, which is weighted by position and accentuation of the search term within the document. This way the relevance of a document for a query is determined. The IR-score is then combined with PageRank as an indicator for the general importance of the page. To combine the IR score with PageRank the two values are multiplicated. It is obvious that they cannot be added, since otherwise pages with a very high PageRank would rank high in search results even if the page is not related to the search query.

The Effect of Outgoing Links on Page Rank

The number of links significantly alters the way PageRank is distributed.

Generally you will want to keep Page Rank to a minimum. (Ridings)

The best outgoing link page is one with low PR and contains many links to to pages on your site.

Stopping PR Leakage

Stop PR leakage when you link to other sites by “writing reviews of the
sites on a separate page, and provide a link to
those reviews along with each hyperlink to the external site. Open review pages using new browser window. Place no other links on the review page other than the link to the home page. A good review page should encourage the site being reviewed to also link back to your review page.

Extra pages generate SEO points
PR Feedback from reviewing sites linking back to you
Keeps more PR inside your site (Ridings)

Adding extra internal links to outbound pages will improve PR. (Ridings)

Each page in the Google index has a vote, regardless of how small.

The more pages you have in the index, the more votes you have. A big website alone won’t cut it. The pages must be in the Google index. (Ridings)

Page Rank Feedback – Sometimes it is good to link to other website pages. The very act of Web Site A linking out to Web Site B causes PR to “feed back” to Site A.

The number of pages, and the structure you are linking to has significant influence on the amount of PageRank feedback that occurs. (Ridings)

Page Rank is a multiplier (0).

When Google penalizes a page and gives it a value of (0), it causes the page to drop because anything multiplied by zero is zero.

Your score from other factors multiplied by your PageRank score of zero, will always be zero (the lowest score possible). (Ridings)

Google ignors artificially created links by removing the link entry from the matrix. (Ridings)

A PR0 page is deduced to zero after actual page rank has been assigned. Therefore another penalty must be assessed if the PR0 page is to be nullified during the PR transition process.

How Page Rank is Calculated

Page Rank is determined by the number of “votes” or incoming links a website has. If website A points to website B, Google takes that to mean that website A thinks website B is important. Page Rank also takes into account the importance of website A. The more important site that’s linking to your site, the better it is for your page rank. Anchor text has no bearing on page rank.

The PR range changes each time Google re-indexes.

Toolbar sometimes guesses, giving page rank before a page is indexed.

Ian Rogers says, “PageRank says nothing about the content or size of a page, the language it’s written in, or the text used in the anchor of a link!”

Jill Whalen, of Highrankings.com feels that PR is a useless measure of Google Rankings and advises one to remove the toolbar altogether.

Google Directory PR

Google Page Rank is visible in the Google Toolbar on a 10 point scale and in the Google Directory on a 7 point scale. It is largely agreed that these two ranking displays “are only a scale of what many refer to as real or raw PageRank.” (Mutch) “These 8 positions are 5/35, 11/29, 16/24, 22/18, 27/13, 32/8 and 38/2.”

“It is only by looking at the source that you can tell that the Google Directory PR of a listing is.” Bob Mutch Article.

Bob Mutch of SEO Company explains that Google has another measure for determining the rankings of a webpage apart from the rankings shown in the Google Toolbar. This ranking system is what he calls the “RPR” or “Real Page Rank” which is the behind-the-scenes ranking system that

Sometimes what you see on the Google toolbar may not be related to actual PageRank at all. (Google can and does, assign whatever toolbar PageRank value they want to assign to a page.) (Ridings)

Rank Weight Factors

An SEO Factor is weighted depending on how many webmasters are manipulating the factor. The more the factor is manipulated, the less weight it has, for example, meta tags. Meta tags are easily and regularly manipulated by webmasters, thus causing the meta tags to have less weight than they once had for overall rankings. (Ridings)

How Google Indexes a Website

Google sends out crawlers to a URL and saves the indexed content in a repository. The indexer parses the web pages in the repository and stores the links in the anchors file. From there the parser generates the links database for the URL.

Google updates its backlinks about once per month.

Quote: While some are claiming that PageRank is going to be discontinued, Google currently states on their Google Technology webpage that “PageRank continues to provide the basis for all of our web search tools.”