The idea behind the Google PageRank algorithm came about at Stanford University in 1996 via an academic paper authored by Larry Page and Sergey Brin.
When Google launched, this was the first major tool that was used to determine the quality of a web page and in part the web site that the page resided on. Later, the process whereby Google determines the PageRank of most pages on the internet was patented under U.S. law.
How Google PageRank Works
The PageRank essentially works much like the popularity of a child at school. Those kids who are deemed “the cool kids” decide who else is cool too. Then as a result of their association with the cool kids, they become cool even if they’re a bit of a nerd.
In the case a PageRank (PR) scoring which runs from 0 to 10 (with a NR scoring for no present ranking), if another web site that is well respected with a PR of 6 links out externally to another web page then that page will rise in the estimation of Google. The more links from quality sources (pages and domains with high PR), the more “cool” the linked to page and site will become. Eventually their own Google PageRank would be adjusted to reflect this new found “coolness.”
Lack of Updates
The importance of Google PageRank is called into question by Google itself. The Google PageRank has not been updated for web sites since December 2013 with the Google toolbar and more than a year with Google itself. Google’s John Mueller commented in October this year:
“There are a few things where we do take action that you might not see directly. Toolbar PageRank is something that we have not updated for about a year now, and we’re probably not going to be updating it going forward… we have a lot of way to recognize these problematic links, and the sites selling those links, that essentially blocks the PageRank from passing through those sites.”
What Predictive Tools To Use Instead Of PageRank?
Moz, the SEO site, offers its own predictive statistics which are updated regularly, based on the search results from Google. These metrics consider linking quality and quantity, as well as a host of other considerations. The metrics from Moz are now used quite widely used by people involved with online business.
Their Page Authority metric measures the likelihood that a web page is likely to be looked at favorably for ranking with Google. A Domain Authority metric also exists which looks at the likelihood that the domain will rank favorably. These operate on a 100-point, logarithmic scale, starting at zero and working up to 100.
The basis of the logarithmic scale, for non-math nerds, is that it is infinitely easier to rise from a rating of zero up to 30 than it is to rise from 30 to 60. Essentially the incline gets steeper and steeper as a better rating is achieved. To that end, a 60 rating instead of a 30 rating is not only twice as good, but considerably better than that.
There are also MozRank and MozTrust scores which amalgamate several metrics into overall ratings. MozRank amalgamates page and domain strength whereas MozTrust looks at the quality of the links rather than how many there are. Both MozRank and MozTrust use a 10-point logarithmic scale from zero up to 10.
Relative metrics can be searched on Moz with the Open Site Explorer.