Of the countless statistics thrown up by the referendum debate so far, one of the most striking must be this:

47% ?¨of people who describe themselves as "Scottish not British" are opposed to independence. In other words, nearly half of those who do not feel British in any way still want to live in Britain.

The figure was highlighted at the start of the year by ScotCen, the Scottish Centre for Social Research, in a report which argued that, for all the patriotic flag-waving we are sure to see over the coming 12 months, national identity will not be the decisive issue when voters to the polls. Rather, ScotCen concluded, we will consider our wallets.

The economy is at the heart of the debate over whether Scotland should become an independent country or remain part of the UK. A poll a couple of years ago suggested that Scots would vote by two to one in favour of independence if they could be sure it would make them £500 per year better off - and by two to one against if they knew for certain they would be £500 poorer. It has not gone unnoticed by the two sides in the campaign, which are already directing their efforts towards persuading voters either that Scotland's economy, and with it their prospects and standard of living, is safer and more secure as part of the UK or that independence would enable it to thrive by giving the Scottish Government the powers it needed to encourage business and win investment.

Central to the economic argument so far has been the question of what currency an independent Scotland might use. First Minister Alex Salmond's plan is to keep the pound within a formal currency union, or sterling zone, with the rest of the UK. Scotland and the UK would share the Bank of England as their joint central bank and individuals and businesses would see little change. The plan was endorsed by the Scottish Government's high-powered Fiscal Commission Working Group, headed by former Scottish Enterprise chief Crawford Beveridge.

The UK government, however, has poured cold water on the idea. Chancellor George Osborne says Britain would be "unlikely" to enter a currency union with an independent Scotland as it would expose UK taxpayers to risks arising from financial crises in another country. The First Minister claims Mr Osborne is bluffing. The UK, he says, would want to be part of a sterling zone the income of which was swollen by Scottish oil, whisky and other exports. He also makes the point that for all their dire warnings, UK ministers have never actually said "no" to a currency union.

The argument does not end there, however. There is also the issue of how permanent a currency union might be. If it was seen as a transitional arrangement, convenient for Scotland in the short term but a stepping stone to a separate currency, it would be a much less attractive proposition to the UK. In terms of the political positioning that is taking place, calls from a range of Yes campaigners - including Yes Scotland chairman Dennis Canavan, former SNP deputy leader Jim Sillars and Scottish Greens co-convenor Patrick Harvie - to consider a separate currency have played into George Osborne's hands.

Those in the Yes movement who favour a new currency do so because of concerns about the impact on Scottish economic policy of formal monetary union. The Scottish Government accepts the arrangement would place some limits on borrowing and debt levels but says the restrictions would not go beyond the sort of sensible financial discipline ministers would wish to pursue in any case. Currency union "would not seriously inhibit" policy freedom, according to the Government's Scotland's Economy: the case for independence paper.

The UK government takes a different view, warning that if a currency union could be agreed, an independent Scotland's spending-and-tax policy would also be limited. Alistair Darling, the head of the pro-UK Better Together campaign, has claimed the entire Scottish budget would have to be "signed off by what would be a foreign government". Again, such pronouncements have been dismissed as a bluff by Mr Salmond. However, Professor John Kay, a former member of the First Minister's council of economic?¨advisors and one of the most eminent economists to study Scottish?¨independence in detail, has also ?¨warned that the UK Treasury seeks "extensive control" over Scottish economic policy and says it would ?¨be hard to negotiate a currency union "consistent with the aspirations ?¨of independence".

Doubts about a currency union have put the First Minister under pressure to outline his "Plan B". He has refused to be drawn but he has issued clear threats that an independent Scotland might refuse to take on its £92billion share of the UK's national debt if it was prevented from keeping a share of its present assets, including the Bank of England. The warning has been taken as a sign that under the SNP an independent Scotland might unilaterally keep the pound without a formal agreement with the UK. There would be nothing to stop "sterlingisation" as it is known but both sides agree it would be an imperfect solution for a country of Scotland's size and economic complexity. Without a central bank, an independent Scotland would not be able to print money and might struggle to respond to financial crises.

Professor Kay dismisses the idea out of hand and believes the most likely outcome of a Yes vote would be the creation of a new currency pegged to sterling. The move "sounds more radical than it is," he says, and would be perfectly workable.

The currency issue has overshadowed the debate about the kind of economic policies an independent Scotland would need to flourish. The SNP's flagship pledge is to cut the rate of corporation tax to 3p below that of the rest of the UK. The Scottish Government claims the move would boost investment and create 27,000 extra jobs over 20 years. In its Scotland's Economy report it says a range of other fiscal powers, from taxes such as excise duty and VAT to the welfare system and public sector pay, could be harnessed to "boost growth, address inequality and stabilise the economy". In addition, powers over regulation, competition law, trade and immigration could be used to boost the economy. Detailed policies are still being drawn up but Finance Secretary John Swinney has already ruled out tax increases for the oil industry and has said he "doesn't envisage" personal tax increases in an independent Scotland.

The Scottish Government argues that the economic powers which independence would bring could be used to assist key sectors such as renewable energy, food and drink, the creative industries, life sciences and financial services. Scotland is a wealthy and dynamic country, ministers argue, but its potential has been stunted by Westminster policies not tailored to its needs. But what if Scotland votes No?

We know for sure that Holyrood will become responsible for levying a portion (about half) ?¨of income tax from ?¨2015 when powers under the new Scotland Act take effect. The Scottish Parliament has already devised its own version of stamp duty as part of the same transfer of powers. In addition, all the pro-UK parties are considering plans to extend devolution, which they will put to voters in the 2015 UK general election if independence is rejected. The Nationalists remain sceptical that anything significant will come of these promises.

Finally, a word of caution. Voters will be bombarded with competing claims about the economy right up until polling day next September. But it should not be their only consideration, far from it. In a rather unexpected conclusion to a lecture at the University of Glasgow this year Professor Kay said £500 plus or minus was at the "outer limits" of what independence might do for people's pockets. "Scottish independence is not primarily an economic issue," he said. "Anyone who goes to the ballot box in 2014 believing either that they should vote no because independence for Scotland would be likely to be an economic disaster, or vote yes because they believe it is likely to lead to an economic bonanza, has failed to review the issues sensibly."