Google PageRank primary function is to evaluate the amount and quality of inbound links to a particular site. Currently, it does not take into account the anchor text or content of the referring pages. This is, however, expected to change in the near future. Google’s main algorithm does not currently involve the PageRank.
According to SEO Administrator, this example below shows how each page has a real PageRank value known only to Google and a displayed PageRank range for their ToolBar. They created a system by using this logarithmic scale:
Real PR ToolBar PR
1-10 1
10-100 2
100-1000 3
ect… ect…
This shows that the PageRank ranges displayed on the Google ToolBar are not all equal. For example, it is easy to increase a PageRank from one to two, while it is much more difficult to increase it from six to seven.
The main purposes of the PageRanking system are to provide a quick check of the site’s popularity and to evaluate the competitiveness level for a search query. Again, remember that a PageRank of a 5 or 6 is a relatively high PageRank. It is highly unlikely that a small business will ever achieve a PageRank of an 8, 9, or 10.