ROLLING Stone Mick Jagger apparently once confessed that while he made most decisions in his life after consulting his head or his heart, when it came to voting he generally relied on his pocket.

And when election strategist James Carville was running Bill Clinton's successful US presidential election campaign in 1992, one of the slogans he chose to put up on the wall was "The economy, stupid!", since immortalised as "It's the economy, stupid!".

Professor John Curtice of the Scottish Centre for Social Research has come up with a similar observation in his latest analysis of the Scottish Social Attitudes survey. The casual observer might assume that in deciding whether to vote for Scottish independence, having a strong sense of Scottish identity would be a key factor. Yet, as Prof Curtice discovered, feeling Scottish, as opposed to British, bears little correlation with enthusiasm for leaving the UK. In fact, while two-thirds of those living in Scotland feel more Scottish than British, only just over half (53%) of this group say they want to leave the UK.

Many seem to share the view of Labour's Alistair Darling that Scotland can be "a proud nation within a wider state". Arguably, the way that devolution has allowed a stronger Scottish sense of self to take root, supports that notion.

By contrast, perceptions about the economic consequences of independence feature far more strongly in Scottish voters' attitudes to the idea of Scotland going it alone. Of the 34% who think an independent Scotland would fare a lot better economically, the vast majority favour independence. This supports the view, already expressed by various commentators, that perceptions of Scotland's future economic prospects inside or outside the Union, will decide the referendum. "As yet, a majority of people in Scotland are not convinced that independence would be of positive economic benefit," says Prof Curtice.

Last week two studies from Capital Economics, the international macroeconomics firm, predicted that independence would carry costs for both Scotland and the UK. Though other think tanks have been more positive about the economics of independence, the Yes Campaign clearly has its work cut out on this front.

Coalition cuts may appear to offer fertile ground for the SNP. Yesterday Yes Scotland chief executive Blair Jenkins suggested this week's benefits cap would be grist to his mill but that will depend on whether an independent Scotland could afford to lift it or whether an incoming Labour government at Westminster in 2015 could offer a brighter future to struggling Scottish households. Meanwhile, current uncertainty about the eurozone and the global economy is not the ideal climate in which to persuade voters to take a leap into the unknown. And most of the Scottish business community will not commit to such a change until they see what amounts to a convincing business plan for an independent Scotland.

Perhaps the Yes campaign would do better to adopt one of Mr Carville's other slogans: "Change vs More of the Same."