Credit where it's due
If you go to a bank looking for a loan, the manager's going to want to see your credit history.
If you don't have a credit history, you're more of a risk, and can expect a higher interest rate.
That's the calculation made by the credit ratings agencies who have been talking to the Financial Times' economics editor, when he went asking what kind of rating an independent Scotland could expect.
The answer was: we're not saying.
It's not as if the agencies haven't made enough enemies already, and they've got their reputations to rebuild after failing spectacularly to spot the dangers of the pre-2008 asset bubble.
But they gave a broad hint that an independent Scotland is unlikely to inherit the UK's triple-A credit rating. The FT's Lex column has already guessed that Scotland could expect Slovakia's credit rating, with the 4.5% interest rates that go with it.
"Immature and unpredictable"
A lot depends on the nature of Scotland's links with sterling.
If there's a deal on running the currency jointly with the rest of the UK (RUK), it could make an independent Scotland a safer bet for investors, and bring interest rates towards those of the RUK.
Without a deal, and no lender of last resort, it's reasonable to assume a higher risk of default, lower credit rating and higher interest rates.
We're told one of these agencies, Moody's, explicitly says countries are marked down if they don't have a long record.
The methodology states: "Immature economic and political institutions increase the risk of unpredictable behaviour in times of stress, inviting negative credit implications".
"Immature and unpredictable"!? Anywhere near Alex Salmond's office, that's fighting talk. We're talking here about one of Europe's ancient nations, with a history of financial canniness that only the Swiss could match, and innovation that even outwits the Swiss.
("RBS's near collapse?" you might well point out. "That was down to poor regulation in London," comes the reply.)
So the Scottish government has hit back, pointing to the credit ratings agencies' reluctance to put their views on the record with the FT.
St Andrew's House has followed through with a torrent of statistics, becoming familiar to those of us who watch such things, and intended to intimidate any bank manager into awarding the best possible rating.
Size of country? No problem. Look at Finland, Denmark, Norway and Denmark.
But haven't those countries got a long track record of fiscal stability? Holyrood's been balancing its budgets since the Scottish Parliament first got a block grant 12 years ago, comes the reply.
Is that because of fiscal discipline, or because there was no option?
One of the problems with this response is that the SNP has complained bitterly that it ought to have the powers to borrow.
And it's not wanting fiscal freedom so that it can generate big surpluses. It wants to borrow to invest, meaning debt levels would go up.
That Scottish government spokesman hits back with talk of an independent Scotland's relatively low inherited debt levels. That's open to dispute, not least with the Whitehall negotiators who would thrash it out.
And to take the number from 2009-10 is not much guide to what an independent Scotland would face, as it shows the UK's net debt at 53% of gross domestic product, whereas the unhappy economic events since then have sent it soaring towards the 80% mark.
The Scottish government's defence of the nation's economic robustness also includes a number that keeps cropping up - a measure of Scotland's wealth.
If you take the product of its economy in any one year, including the oil and gas pumped from under its waters, the OECD figures suggest Scotland could have the sixth highest gross domestic product per head.
But there's a catch there.
For that number to be meaningful for the average Scot, and for the government to be able to borrow against it as an asset, that oil and gas would have to be in public ownership.
The benefit of that oil wealth is for the companies that own it, and very little of it is owned by companies based in Scotland. Only the tax revenue and the associated jobs would be to Scotland's benefits - unless, that is, it gets nationalised, and that would come at quite a price.
A similar tale can be told of all the investment going into renewable energy. With the notable exception of SSE, most big investors are from outside Scotland, and will repatriate their profits.
Perhaps the more meaningful figure would be gross national product, which adds overseas earnings for Scottish-based companies while subtracting profits that leave the country to the bank accounts of overseas owners.
That gets to a number a lot closer to Scotland's real wealth, and some way below number six, and closer to the UK in the hit parade of wealthy nations.