If you visit my SEO DIRECTORY you will see that it has a hp PR of 1 all internal pages are indexed with a PR3 or PR2. The hp has around 1300 links coming into it but because I was not picky enough on who is linking to me I was punished in google. Now if you take a look at my SEOTeam.ORG You will notice a nice PR of PR4 btw it has only been online for a month or so. The backlinks are ooo kkk but not BAD which I think has catapulted my seoteam.org into a pretty darn good PR position!! BTW anyone looking for a free one way link from a PR 3 seo tips directory please go to www.directoryrevolution.com/forum2 and sign up and post a message and I will give you a free one way!
Also has to do with the aging of the backlinks. At this point I dont think anyone really has a clue, at least since the last few updates.
Not only the age but the quality of the back links... I have been experimenting with google bowling and I havnt seen any results yet as i am still testing but it should work. See my blog for more info on google bowling. Yes SEOTEAM.org does redirecto to webmastermydomain.com.. I do sign advertising with seoteam.org because its shorter
PageRank is a purely mathematical calculation and has nothing to do with age of links or link relevancy or anything like that. The PR of the link to your site and number of outgoing links on the page are what matters. A link from 1 PR5, no matter the relevancy, is better than 1300 PR1's FOR PR PURPOSES. Now as far as rankings go, I'd probably take the 1300 PR1's. Also there is something strange with new site's PR and Google where many sites that don't deserve PR4 or 5 are now showing them. I have a few myself. Not sure if that's what's going on with your site or not though.