You keep switching between flows and stocks and what you want your numerator and denominator to be, why wouldn't I just look at real spending and real debt numbers - ie. the number we ultimately have to pay interest on?
GDP % is only relevant if we are politically able to raise taxes.
Both of the charts I posted have GDP as the denominator (although I incorrectly said the first was “share of budget”).
I think it’s very important to use GDP as a denominator, because otherwise you’ll be stuck crying wolf, saying “debt always keeps going up” even during the good times.
There are a lot of people who simply don’t believe that the government budget needs a trim right now, because people have been continuously saying there was a debt crisis even when the financial situation was relatively favorable.
GDP % is only relevant if we are politically able to raise taxes.