OK so my question on Pagerank is not about the 'merits' or otherwise of it which has been discussed countless times before. It is about how links age over time. I've never given this much thought really but took a look at a couple of old site I have today. Both were PR 3 and have been for a good couple of years. They have maintained this ranking though the last 18 months of updates until the latest Feb update. The homepage value for both has dropped to 2 and many of the inner pages are 0 or have no PR assigned according to the PR toolbars in my browser. So I guess the link profile was mixed - both aged and potentially 'maturing' links to each site and also more 'spammy' links which have no doubt been lost overtime. Links were built to both the domain and heavily to inner pages. However I was interested that the latest update saw such a drop off. Does anyone think the calculation for PR may have changed with the last update or is this merely a coincidence to see such a sudden drop off - or is something else at foot?