Rich and all,
Dont you think the uW/sq cm is a more important figure the 3%, 5%, 7% etc. Thanks to some old posts I found, i belive it was Merlin, who linked the uk UV site, great info. Maybe, if it hasn't already been done, someone could write a dunnies guide to UVA/B, who what where when and the important numbers.
They have Tube info here (
http://www.uvguide.co.uk/fluorescenttubes.htm)
Two graphs of interest, under the tubes section, are Burn-in (shows a 10% decay in 100 hours) and the long term decay of nearly 40% in a year.
I sound like a salesman . . .