Google says Scotland’s GDP is $216bn. We don’t know what the national debt will be (all those unknowns – and let’s face, a UK-exScotland government would try to stuff as much debt onto Scotland as it could); the Guardian reckons it could be £81bn plus potential liabilities from a share of RBS and HBoS of a further £100bn. At $1.6/£, that is $130bn plus $160bn – a total of $290bn. The debt:GDP ratio is therefore 60% or 134%, excluding or including banks.

Denmark’s GDP is $333bn – 50% more than Scotland’s (so Denmark’s population is 50% more productive). The level of Danish national debt is 47% of GDP – much lower than Scotland’s, even excluding bank liabilities.

So if you wanted to lend someone £14bn per year (the Guardian’s estimate of Scotland’s annual borrowing using an optimistic split of oil revenues), would you lend it to Denmark or Scotland – who have to work 50% harder to pay it off?

Scotland would have to pay a lot more than Denmark to fund the debt. And of course Scotland has LESS money with which to pay that interest – so debt interest as a proportion of GDP is way higher.

(All figures quick and dirty, and I have no idea if they are truly comparable!)