Should we mind the gap, the "fiscal gap" that is?

Yes, say the respected Institute for Fiscal Studies.

The fiscal gap is the term they give to the amount they say an independent Scotland would have to find to make her finances stable.

IFS researchers say that Scotland would have to find some £6 billion in increased taxes or public spending cuts to reduce debt to a respectable 40% of national income.

This is how their report puts it:Our basic model for Scotland (which assumes that Scotland takes on a population share of accumulated UK debt at the point of independence) suggests that, without policy action, public sector net debt in Scotland would increase every year as a share of national income and exceed 100% of national income by 2033–34. We estimate that Scotland would require a permanent tax increase or spending cut (or a combination of the two) equal to 4.1% of Scottish national income (or about £6 billion in today’s terms), to be implemented in 2021–22, to put Scottish public sector debt on course to reach 40% of national income by 2062–63.

So, an independent Scotland has a problem then? Well, when a independent (small 'i') group like the IFS says there is a problem, few will challenge them.

This report is, therefore, a setback for the SNP which will launch its blueprint for independence in just over a week's time.

However, the SNP's minister for finance, John Swinney, challenges this conclusion.

Mr Swinney says that the IFS report only reinforces the SNP's case for independence.

It proves, he says, that Scotland needs to have control over the fiscal levers of power to it can, to borrow from the IFS, close the gap by promoting economic growth.

Mr Swinney puts it thus: “The IFS themselves admit their projections in this report are ‘inherently uncertain and could evolve differently if Scotland were independent rather than part of the UK; in addition they could be substantially effected by the policies chosen by the government of an independent Scotland’.

“The whole point of independence is to equip Scotland with the competitive powers we need to make the most of our vast natural resources and human talent and to follow a better path from the current Westminster system which stifles growth and which is responsible for the damaging economic decisions which this report – and its projections – are based on.

We will be hearing more from the finance secretary tomorrow when he sets out "the choices available to increase productivity and economic growth in an independent Scotland".

So we can expect some further response to the IFS.

And the answer to the question? Yes, we should mind about the gap. And take great care analysing the IFS paper and the SNP's response to it.

Here is the IFS press release to get you started:

http://www.ifs.org.uk/publications/6950