To me, the idea that it's "political" to use the US debt, is on its face hard to believe or take seriously. So before everyone else has to justify every other claim down to many levels of detail, can we see any justification of the claim that there's any disadvantage to using this convenient number, or that it's done for political reason? Occam's razor suggests it's just being used because it's convenient and easy to use and meets the criteria, and once it got into the mix there was no reason not to keep it the next year, or the next. It's easier to keep things that still work, than it is to spend extra time searching for replacements for no particular reason or advantage. -- Cos