Page Rank Optimization

This two-part guide will introduce you to page rank and page rank optimization (page rank sculpting) of a website using internal link structure. In the first part of this article we’ll explain what page rank is, how it works and how it’s distributed, while the second portion of the article will focus on page rank sculpting.

Google and Page Rank

Page rank was invented by Google’s co-founder Larry Page (hence the name Page Rank) as a way of determining the  importance of web pages. At the time page rank was invented, search engines relied on text analysis, meta tags and on-page criteria, all of which were easy to manipulate. Early search engine optimization companies employed coders who reverse-engineered algorithms in order to produce high-ranking pages at will. Page rank made it possible to calculate the importance of each separate page on the web, rendering many on-site SEO techniques useless.

For more information on page rank check the following sources:

  • http://infolab.stanford.edu/~backrub/google.html

  • http://en.wikipedia.org/wiki/PageRank

Relevancy vs Importance

It’s important to understand that page rank does not compute relevancy, only the importance of each page. When a user makes a search query, a different algorithm calculates the relevancy of page, while page rank simply selects the most important result.

User enters the search query.

Google selects results that contain the search term (aka keyword).

Selected results are sorted by page rank from the most important to least important results,

Results are displayed to the end user.

Different algorithms are responsible for relevancy calculations. From an SEO perspective, keywords in anchor text, title tags and content are some indicators of relevancy.

It’s important to understand the difference between real page rank and tool bar page rank.

  • Toolbar page rank (TBPR) can be tracked using the Google toolbar. Toolbar page rank shows results which are several months old. TBPR numbers (from 0 to 10) are heavily inflated, since real PR numbers are not linear. For instance, a page with a PR 8 would logically have twice as much PR as a page with PR 4. In reality its page rank is usually several times more.

  • Real page rank is a number we can only guess, since Google is a black box when it comes to disclosure. Imagine a rising slope, which increases until it reaches a vertical position.

Toolbar page rank is calculated using ranges of real page rank. For example, imagine that the maximum Google PR value is 1,000,000. Toolbar PR 1 equals a range of 1 – 10. Toolbar PR 2 equals a range of 10 – 50. Toolbar PR 3 equals a range of 50 to 1000. Toolbar PR 4 equals a range of 1000 – 10,000 and so on, until finally toolbar PR 9 ranges from 600,000 – 1,000,000.

As you can see, going from one to two on toolbar PR is far easier than reaching 6 or 7, as the actual numeric values for those ranks are 100 times higher.

If you ever played any role playing games (such as World of Warcraft), you will know that the earliest levels are easiest to reach. As you progress to the upper levels, it gets harder and harder to go up a level, because the overall score requirement goes up as well.

Level

Score Required To Obtain the Level

01-10

500

11-20

1,000

21-30

2,500

31-40

4,000

41-50

6,000

51-60

9,000

61-70

13,000

71-80

23,000

81-90

43,000

91-99

83,000

As you can in the example from America’s Army, level requirements go up as you progress. Toolbar page rank relates to real page rank in a similar way. On the toolbar, two pages may have a rank of 8, but their real Page Rank (score) is different; a page with a higher real PR number will win on search results.

Also, keep in mind that toolbar PR is updated every few months, while real page rank is constantly renewed and recalculated, making toolbar page rank sort of a "snapshot."

Keep in mind that page rank was invented more that 10 years ago; Google has made modifications to the formula since then. Google also released Trust Rank, Topic Sensitive Page Rank (TSPR) and MANY other algorithms. We can assume that page rank is still one of the most important ranking factors, but don’t build your entire campaign around this single measurement.

The Dampening Factor

Page rank is built on the principle of following links, resembling a random Internet user who follows all links he sees. The more links point to X page, the higher the chances of that random user finding the X page by following all the links he sees (hence links provide a clue to the importance of each page).

But what if the random user gets tired of following all the links and closes the window? This is the purpose of the dampening factor in the page rank algorithm. It comes in handy exactly at times when the user becomes "tired" and stops following the links (or stumbles onto pages that don’t have any links to other pages).

According to Wikipedia, if a page has no links to other pages, it becomes a sink and therefore terminates the random surfing process. However, the solution is quite simple. If the random surfer arrives at a sink page, he picks another URL at random and continues surfing again. When calculating page rank, pages with no outbound links are assumed to link out to all other pages in the collection. Their page rank scores are therefore divided evenly among all other pages. In other words, to be fair to pages that are not sinks, these random transitions are added to all nodes in the Web, with a residual probability of usually d = 0.85, estimated from the frequency that an average surfer uses his or her browser’s bookmark feature.

Pages Voting for Themselves

There is no actual proof as to whether pages can vote for themselves (i.e. URL site.com/page.html has link to site.com/page.html). The only thing we can do is guess that this sort of vote is impractical and is discounted by Google.

Page Rank Flow

If a page with PR 4 links out to eight pages, than each page that received a link gets 0.5 PR points. If that same page with links to only four pages, then each page gets 1 PR point. The distribution model is equal, meaning that points are equally divided between pages. The fewer links there are, the more page rank power is passed and conversely, the more links there are, the less PR is passed to all pages.

Not that pages do NOT lose page rank when they link out. Linking out merely distributes page rank values. For example, when a page with PR 5 links out to 10 websites, it does not lose its page rank, it simply distributes it, while keeping the actual value to itself.

More Than One Vote from a Page

We can assume that Google only counts one vote from a unique page and discounts duplicate or triple votes. For instance, if X page with a page rank of 4 has two links to A and one link to B, then the distributed page rank is 2 per each page, discounting the duplicate link.

This is an assumption. For further proof you can run your own tests.

Page rank is accumulated from inbound links and is distributed with outbound links. The more inbound links a page has (internal and external), the higher the rank of that page, assuming all other link quality factors are met (such as the quality of the external website and the trust level).

Initial Value of the Pages

Each page is assigned an initial value, equal to a fixed number. For the purposes of this example let’s use one as the default value assigned to pages. With the effect of the dampening factor, that value goes down to by 0.15 to 0.85, thus the default page rank of each new page (or page without any inbound links) is 0.85.

This also means that new pages (or pages without links) can pass 0.85 of total page rank to other pages. It also means that by increasing the number of internal pages and by directing their links to the most important pages, you can increase your PR.

For new pages to be awarded a default page rank score, they need to meet certain quality qualifications in terms of content, format, keywords etc. In other words, you can’t create a bunch of duplicate/blank pages and raise your PR.

Page Rank Formula

I personally get a sleeping reflex at the sight of equations and formulas, but if math or physics is one of your strengths, check out the page rank formula below.

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

Some of the values explained:

  • PR - page rank.

  • A – page A

  • (1-d) – dampening factors.

Conclusion

Some of the key points to remember:

  • Page rank is a measure of importance, NOT relevancy

  • Tool bar page rank does not give an accurate representation of page rank.

  • Each page is given a default page score of 1 (or whatever Google uses internally).

In the next article we will go into detail as to how page rank works on the site wide level, the distribution of PR between pages, how to highlight important PR pages, page exclusion, the use of no follow in page rank sculpting and more.

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