What does Scotland get out of Scotch? No one really wants to talk about this delicate subject. Newspapers are bombarded with good news press releases from the Scotch Whisky Association (SWA) about £150 per second being earned by whisky with the inference that it is for Scotland's benefit.

A recent article “Scotch Myths” by Colin Donald, the Business editor of Glasgow’s Sunday Herald, finally raises this important issue provoked by a report published by the SWA - ‘Scotch Whisky – The Jobs, The People’ - which promotes the benefits of whisky to employment in Scotland.

Professor John Kay, the UK's most influential business economist writing in Scotland's Economic Future, claims "There are two big questions about the whisky industry in Scotland that need to be answered:"

"One is how well is this industry actually doing, and the other is how much does it contribute to the Scottish economy. I suspect the answer to the second is very little. There needs to be a proper debate about this, not just the usual self-congratulation to which we Scots are prone."

To the first question, recorded jobs actually decreased by 6% in 2010. And long-term production actually decreased in 2010 by 29 million litres.

"Value added from Scotch whisky is reported as around £3 billion – about 2.5% of Scottish GDP – but this figure reflects essentially arbitrary transfer prices and export valuations,” writes Professor Kay, “wages and salaries and purchases of goods and services used in whisky production amount to only about £400 million. To this should be added the returns to beneficial Scottish ownership of whisky-related assets. With retail sales of whisky around the world totalling perhaps £25bn, the Scottish economy appears to derive modest benefit from its most famous product."

Professor Kay's point is that a mere 2% of the global retail sales value of Scotch whisky ends up in Scottish pockets. The reason is that more than 80% of the whisky distilled in Scotland is foreign-owned and the majority of value of leading brands values is accumulated overseas.

The SWA quote the headline figure of £3.9bn ‘gross value added’ (GVA) - the £150 per second - but this has "no significance whatever from the point of view of the Scottish economy," says Professor Kay.

Gross national income (GNI) is more relevant. The GNI, Kay says, should combine the earnings of those who work in the industry, plus Scotland's share of UK corporation tax, plus the dividends and retained earnings of multinational drinks producers accruing to Scottish residents. And to this, more difficult to assess, should be added Scotch whisky’s value to "brand Scotland" - essentially tourism.

But apparently no such figure for the whisky industry has been produced. In Richard Marsh’s report for the SWA, his calculation of the total annual taxes paid to the UK exchequer by the whisky industry was £282m.

Kay says the SWA is “a Rolls Royce operation” at brand protection - few would doubt that - but “its priorities are not interchangeable with Scotland's”, because membership is dominated by multinational giants who have no reason “to maximise Scotch for the benefit of Scotland.” Scotland should wise up to the fact that "lots of governments are making lots of money out of whisky – just not ours.”

He believes Scottish ministers have no idea how the economics of whisky could actually help an independent Scotland. An export tax on foreign owners? A tax on water used to make whisky? Such suggestions horrify CBI Scotland - as much as it does the SWA - but it’s probably coming.

The horse has, I am afraid, already bolted, but expect more on this subject as Scotland’s future as a part of the United Kingdom is debated over the next couple of years.