JUST how wealthy is Scotland compared with other countries?

Are we more prosperous than our neighbours? Are our living standards better or worse than people in the USA, or Norway, or Ireland, or, for that matter, in England?

These are becoming much more than mildly interesting academic questions as we hurtle towards the referendum. If Scotland was seen as an economic powerhouse surely that would translate into public confidence about its prospects as an independent country? And, by the same token, might not news of economic frailty breed caution? In short, would it not be really useful if we could place ourselves on a global rich list?

The Yes campaign certainly believes so and for a long time now have been hammering the message that Scotland is one of the world's wealthiest nations. The sixth richest, to be precise, when figures for gross domestic product (GDP) per capita in 2010 told that particular story. Then it became eighth richest when the 2011 figures put Ireland and Austria ahead of us on the leaderboard with Luxembourg, Norway, Switzerland, the USA and the Netherlands. A bit of a slip but not bad and, crucially for the Yes camp, comfortably ahead of the rest of the UK in 16th place.

This looked like a strong point to be making until the Centre for Public Policy for Regions chucked a spanner in the works.

Last year, the Glasgow University think-tank pointed out that GDP is all very well as a measure of the size of the economy but it is a pretty crude gauge of people's living standards as it includes wealth that's not retained in the country.

In Scotland's case that's likely to be quite substantial, given the number of big oil, energy and drinks companies that are foreign-owned. It's a pattern that is not uncommon in small, open, developed economies - Ireland is a good example - and, argued the CPPR number crunchers, a different economic measure known as gross national income (GNI) would give a more meaningful picture of the country's wealth and what it meant for living standards.

Where GDP shows the total value of goods and services produced in the country, GNI counts goods and services produced by home-owned enterprises. No-one disagreed with the CPPR; the trouble was no-one had any idea what Scotland's GNI might be as the statistics did not exist.

Until last November, that is, when the Scottish Government quietly published some experimental GNI figures and John Swinney began using them to make the case for independence.

According to the figures (which cover 2010), Scotland would be 10th in the world for living standards, a relatively modest drop of four places compared with the GDP per capita ranking and still ahead of the UK in 13th place.

The figures were seized on by the SNP as evidence Scotland was doing better than the UK and, to quote one press release, were "further evidence that Scotland has got what it takes to be a successful independent country". It would not be a complete surprise, then, to see these experimental figures reworked as a Yes Scotland slogan in the not too distant future.

The CPPR, however, has raised concerns about the accuracy of the GNI statistics. In a paper yesterday, economists John McLaren and Jo Armstrong said Scotland's GNI looked a tad high, suggesting it rested on "what appear to be bullish assumptions" about the level of profits which stayed in the country. If you were to look at living standards in terms of disposable household income, for example, Scotland would slip to 16th in the world, below the UK position. Such a fall would be in line with Ireland's experience.

Behind the scenes, the CPPR has been trying in vain to get more information from the Scottish Government about how its GNI figures were calculated. Ms Armstrong told a press conference in Edinburgh yesterday there should be plenty of time between now and September to iron out any flaws and, hopefully, ensure these politically sensitive figures are reliable. Cynics, I fear, will not be holding their breath. More likely they will be expecting a dry Scottish Government press release, around 7pm on Christmas Eve, announcing "methodological improvements" to the statistics.