Google's PageRank Value
Before Google, the search engines and directories listed their web page discoveries, often enough in alphabetical order. Google's PageRank™ formula changed all that as a powerful way by which to rank the value of web pages. PageRank™ is based on the total value of all the inbound links to a page. The more webmasters who vote their approval of pages on your site by connecting a links to them, the higher the ranking of your web page. Webmasters get to vote on how successful your page will be ranked by linking to it.
The PageRank formula dates back to it's early beginnings as a Stanford university project that blossomed into Google. Google displays a PageRank value on it's tool bar which can be installed for free. The tool bar's PageRank value, on a scale from 0 to 10, relates to the PageRank formula much like the Richter Scale's magnitude relates to an earthquake's intensity. In terms of links to your site, an incoming six is worth one hundred incoming fours. It is just a bit more complicated than that, but not by very much.
The PageRank value gets factored against the success of the search criteria and a lot of other things. Google states that there are over 100 ingredients in the recipe. PageRank is one of the larger chunks in a stew. It's contribution to the ultimate ranking in a Google search has changed over the years and appears to have assumed a stronger role a couple of years ago. If none of the pages on your site includes one of the words in a search, then none of your pages show up regardless of PageRank. Content is another chunky ingredient in the mix. Content also contributes to PageRank by attracting links to your site which is the primary fuel that drives the PageRank engine.
The PageRank Formula:
A common way to do computer models is with a mesh of cells with each cell assigned the same calculation to perform, based on the inputs from other cells in the mesh. The current values of all the cells remain the same until each cell has calculated it's next value. At that point all the cells update to their individually calculated values and the next crunch can begin. The calculations iterate recursively recursively until an acceptable degree of equilibrium is achieved.
The PageRank formula is very simple when applied to a single web page. Referring to the diagram at the right, the PageRank sum is the total of all the incoming link values determined by the outgoing formula of each contributing page.
All the outputs from a page have the same value which is the PageRank Sum multiplied by 0.85 and divided by the quantity of outgoing links. Google refers to the 0.85 as the damping factor.
There is no penalty in the formula for outgoing links. However, we cannot determine if outgoing links cost anything until we build a somewhat realistic model and iterate the calculations several times.
Lets model a website:
Simple Website Model
The simple website example at the right consists of three pages linked together. Only the home page has an external incoming link. The Links page can only be reached from page 2 and has five outgoing links. The color saturation indicates the relative score of each page. The thickness of the arrows indicate the relative energy flow.
For each iteration of the model, the Home Page passes 1/2 of it's value to page two and half to the link leaving the site. For this discussion 0.85 damping factor is ignored. Page 2 passes 1/3 of it's value to each of it's outgoing connections. The Links Page passes 1/7th of it's value to the Home Page and to Page 2 and 5/7ths to the five external outgoing links.
The following table shows the score after 15 or more iterations of the model. Note the difference when a link is added from the Home Page to the Links Page. The link exchange between Page 2 and the Links Page is benefiting the Links Page more than Page 2.
|Home Page||Page 2||Links Page|
|11.6||5.1||1.4||No link from Home Page to Links Page|
|11.6||3.8||4.4||Add link from Home Page to Links Page|
The above experiments were done with Excel. You can conduct your own experiments using Web Workshop's PageRank Calculator. Some of the "experts" on the internet will tell you that outgoing links don't cost you anything, based on the PageRank formula. At the molecular level, that is true of the model. However, when the formula is built into a respectable model and iterated several times, it becomes apparent that outgoing links do drain energy off the site.
Insights From the Model
A few insights can be drawn from the very simple website model, especially if we experiment with a few more variations:
- The more pages the higher the score.
- The more interconnected the site, the higher the score for each page.
- Interconnections can be structured to retain the same site total, while boosting selected pages.
- Pages with more incoming connections (external or internal) will rank higher.
- Pages with more links leaving the site will be less valuable to the rest of the site.
- Reducing the number of links exiting a page increases it's value to the site.
- The larger the site, the less of a drain will be the Links Page.
- The Links Page should link to every page on the site to reduce it's outgoing ratio.
- The cost of a few outbound links here and there is small on a well interconnected large site and more costly on a smaller site.
- Adding a new Links Page can add some value to the site simply because adding pages adds value, but not as much as a new page with no outgoing links.
When soliciting links for your site:
- The best link come from a site's most popular page, regardless of whether it is called the Home Page.
- Links from a popular page are more valuable than links off a Links Page.
- A top quality link can be worth more than a dozen or more low quality links.
Outgoing cost and link exchanges:
The PageRank formula does not penalize the outgoing links. However, we have seen that outgoing links do bleed off energy as we iterate a simple site model. One expert on this topic has calculated that the PageRank benefit passed on to other sites equals the page loss of the contributing site.
When somebody solicits a link exchange with you be careful that you are not providing a high quality link in exchange for a worthless or low quality link. Ask for the path to the page where they propose to place the link to your site. If it is a buried page with 100 other outgoing links it's value will be virtually worthless. You may have a links page on which to feature an equally worthless link in exchange. But why bother. Do save your outgoing links for the sites that really deserve to be linked to and feature them on the appropriate page of your website. Do be a good neighbor on the internet.
If should be obvious by now that link farms are very close to worthless. Few sites link to them, so their value is very low and that small value is divided over a large spread of outgoing links. Some of the more flagrant link farms catch Google's attention and end up getting black listed. Links from such sites are virtually worthless and do not penalize your site. Linking to such sites can cost penalty points. Google cautions that webmasters should be careful who you exchange links with.
Is it a good idea to split a website across two domains? Since PageRank is a page based calculation (not site oriented), it should make no difference if you split your site across two domains with the same links between the two sets of pages. It is possible that Google may apply a relevancy filtering penalty for some links between the two domains that would not be applied for a common domain. There is nothing to be gained by splitting up a site if your objective is to score better with Google. If anything, the single site is the better idea.
Link Popularity Tools
One way to track down candidate directory sites to submit to is to find out who links to sites similar to yours. Find out who links to them using the following two sites:
Link Popularity for Altavista, Google and HotBot
Adme Link Popularity Checker for MSN and AllTheWeb search engines
Google Indexed Pages
Here is how you find out which pages on your site have been indexed by Google. In Google, enter the following in the search box: site:MySite.com Google will return a list of all the pages that it has indexed.
Sites Linking to My Site
In the Google search box, link:www.MySite.com will list the pages that link to your site. Google only lists the higher ranking incoming links with PageRank scores of four and above, perhaps as low as three. Here is a much more comprehensive way to find out what sites Google has listed as linking to your site, by entering "+www.MySite.+org/" into the search box. Change the "+org" to "+com" or what ever, as necessary.