According to preliminary information during the creation of PageRank, Google says it was a probability calculation.

This is the probability of finding a web page from a different page of some sort (in theory).
That is, the more you’ll be on the internet with links to many partner sites, plus you’ll get a higher pagerank.

From this simple calculation system, Google would have implemented succeptibles other variables to vary your pagerank. For example, common sense suggests that GOOGLE systems aim to eliminate cheating as some rings of links, link farms, some directories …
Indeed, for this calculation has a value, it is necessary that your partner is not motivated by a desire to exchange links but a real love for your site.

Note:
- The maximum PageRanks (PR9 and PR10) are assigned to certain well-known sites. For pages belonging to Google, we can explain this by the fact they are the gateways to their world of computing. Their pages are the first to be visited for the calculation of PR, so the probability of finding them is close to 1 (ie a maximum pagerank).
For other sites with very high pagerank, there are many phenomena interact. PageRanks are large sites with numerous partners internet, but not necessarily, it seems that some sites (such as yahoo.com, some engines, directories and other “site selectors”) also serve as gateways to the system calculation of google. In other words, Google looks for its neighbors the sites themselves have defined as important.

Problem:
How the pagerank is it indicative of the relevance of the information that Google search?
As we have said before, nothing, if link exchanges are intended only as increased pagerank. For example, a search on “spuroline” it must first give the big sites that will give scientists the details on the composition of the algae, or small sites hustlers trying to solve the famine in Africa.
There is an increased awareness of the real political problem posed by Google in its near-absolute monopoly. Even if the engine of choice is always searching for the truth as sincere as possible in its answers. How to meet its vision set, of course, champion of democracy, but equal destructive minorities.
Moreover, we should remember the huge amount of information available to both GOOGLE websites that queries executed by users. Imagine the political strength of a company that knows your expectations, your dreams, your concerns, your search in real time across the individual and the world.

The pagerank is a clue to your degree of integration into Google ™ internet.