Halfdeck - 11:19 pm on May 30, 2007 (gmt 0)

"The conclusion from your comments would appear to be that the reason a page goes supplemental is that the individual TBPR for that page is too low, below a threshold? say <2"

Not exactly. Assuming all PageRanks of webpages on the Intraweb adds up to 1, average PageRank is miniscule, something like 0.000000100204023934. Two pages (12+ months old) might both display 0 in the toolbar but internal PageRanks for them may be dramaticly different.