Originally Posted by etechdesigns Google PR is not entirely based on the number of backlinks. Other factors like quality and relevancy of those links, page content, domain age etc. also do count in the calculation of Google PR.

I'm not exactly sure whether thats true or not ( Only google engineers will know for sure). However I believe PR is based purely on backlinks and the PR of the backlinks - i.e you could get a PR 4 site from a single link from a PR 5 webpage.

However (and this is a big however), PR has little to do with your position in the search engines - eg my a PR 4 website, which gained its PR 4 from a single link off a PR 5 webpage is very unlikely to do well in the search engines and is likely to come a lot lower than a site that got its PR 4 from hundreds of PR 0, Pr 1, Pr 2, Pr 3 links.

The reason that most sites ranking higher if they have a higher PR is that they have gained that PR from hundreds of good quality links, rather than a couple of high PR links.

So really PR is a bit of a red herring when coming to ranking - which is what it is all about anyway. Its far better to get links from well trafficed websites which in turn have gained their PR naturally.