So I'm still not 100% convinced that I understand the baseline in a comparative sense, but this article by Harjot Kaleka did at least make me realise that PR is exponential
Note: The scale of 1-10 on Google is not linear. It is exponential in nature, believed to be a base of 6 to 7, that is, PR 7 website is 6 times more important than PR 6 website.I am therefore assuming that PR6 is 6x more important to PR5 and so on. i.e. PR1 (1), PR2 (2), PR3 (6), PR4(24), PR5 (120), PR7 (720) etc... Someone stop me if I'm wrong!