The Big Question: Is Alex Salmond right to believe that Scotland will be independent by 2017?

Why are we asking this now?

Alex Salmond, the Scottish First Minister, has announced that the SNP's new target is full independence within 10 years. It is the first time since the SNP victory in last May's elections in Scotland that he has set a deadline for withdrawal from the UK. Making Scotland attractive to foreign investors will be "much easier" if it is independent by 2017, he said.

It is not the first ever target date set by Scottish Nationalists. In the early 1990s, they had a slogan "Scotland Free by '93", of which the late Donald Dewar said: "It's a good slogan. It rhymes, and they can revive it every 10 years." In 2000, having missed the first target by seven years, gradualists in the SNP persuaded their more impatient colleagues to settle for independence by the 300th anniversary of the union with England, in 2007. Opponents derisively suggested a new rhyming slogan: "Nationalist heaven by '007" – a reference to the most famous supporter of Scottish independence, Sean Connery, the original screen James Bond.

Mr Salmond's target is more serious for the simple reason that the SNP has won its first Scottish election and wields power in Scotland for the first time.

Why did Mr Salmond say this now?

This week, Mr Salmond came forward with a 10-year strategy to turn Scotland into a "Celtic Lion", emulating the success stories of other small European nations like Norway and Ireland. But to achieve it, Mr Salmond said, he needed to cut taxes now controlled by the Treasury. By producing an economic plan and a target date for independence, both at the same time, Mr Salmond cleverly implied that home rule and economic success will be inexorably linked.

But there is another aspect to the timing of Mr Salmond's unexpected announcement – and a cynic might think that this was what really motivated him. Yesterday was Budget Day in Scotland. Therefore it was the day when Scots would be reminded of the promises the SNP made in the run-up to last May's election, such as those to abolish business rates for small firms, to reduce class sizes to a maximum of 18 pupils during the first three years of primary school, to cancel student debts, and to hire 1,000 new police officers.

So far, Scotland's police forces have been given the money for 500 extra officers; negotiations about class sizes are still going on; small firms were told yesterday that their business rates will disappear "in due course"; and the promise to scrap student debts was shelved.

How much the Scottish finance minister, John Swinney, can spend depends on the size of Scotland's block grant from central government. The SNP claims this year's settlement was the worst since devolution, whereas the government insists it was generous. Yesterday, Mr Swinney persuaded Scotland's 32 councils to freeze council tax this year. By flying a kite about the date for independence when he did, Mr Salmond drew attention away from the budget crisis.

Would Scotland be better off without England?

There has been a long and unresolved argument in Scotland about what would happen to its economy outside the UK. Ask two Scottish economists, and you will get three opinions.

The most authoritative source for the study of this issue is the annual GERS (Government Expenditure and Revenue Scotland) report. The most recent, published last December, said that Scotland received 9.7 per cent of all UK government expenditure, although it is home to only 8.5 per cent of the UK population. The UK government spends £11.2bn more per year in Scotland than it takes in tax revenues. In other words, Scotland receives a subsidy from the rest of the UK equal to 12 per cent of its GDP, which it would lose if it left the UK.

But these figures are compiled on the basis that North Sea oil belongs to the UK as a whole. If, say, 90 per cent of the oil was designated as belonging to Scotland, that figure of £11.2 billion would fall by almost half, to £6.5 bn.

Mr Salmond argues that with the oil revenues coming to Scotland, the country could pay its way. And if you ask what happens when the oil runs out, Mr Salmond's answer is that there is still about 38 million barrels' worth of black gold under the sea – enough to last a very long time. Others dispute whether there is that much oil, and whether it would be economic for the oil companies to extract it all.

Would England be better off without Scotland?

Scottish devolution has set off a reaction in England. English people ask why we still apply the so-called Barnett Formula, which guarantees that Scotland always receives a proportionately bigger slice of public spending than England.

The Scots have a range of treatments available free on the NHS that is denied to the English, including free eye and dental checks. Prescription charges are cheaper north of the border. Student tuition fees are lower, and more pensioners are entitled to free bus travel and to have central heating installed for free.

Another, even hotter issue, is the so-called "West Lothian" question. At present, Scottish MPs such as Gordon Brown and Alistair Darling have a say over the health and education systems in England, but English MPs have no control over these functions in Scotland.

The Conservatives, who have only one MP in Scotland, say that Scottish MPs should be excluded from voting on English health and education bills. But this could turn the House of Commons into a hybrid that is controlled by Labour when it is discussing the Budget, or defence or foreign affairs, and controlled by the Conservatives when it comes to health and education. Even the Conservatives – who would be the big winners in England if the UK broke up – do not want it to happen.

The English may be exasperated with the Scots, but most do not want a divorce. England, alone, would struggle to retain the influence in the world that the United Kingdom has.

Would it be easy to undo the Act of Union?

Suppose the United Kingdom did split, and Scotland became the 28th state to join the EU, there would be huge arguments over detail. Would the Scots, for instance, take on a share of the UK's national debt? And if so, how big a share? Would they accept the full cost of cleaning up the sites of their nuclear power stations, or would they want a contribution from England?

What about the Trident nuclear submarine base at Faslane, on the Clyde? And above all, who would own the oil? The SNP says that 90 per cent of it belongs to Scotland. The English might not agree. And of course, there can be no progress towards independence unless the SNP is in power in Scotland to push for it. Plus recent studies suggest that fewer than one Scot in four supports independence.

Would Scotland be better off without England?

Yes...

* As an independent state, Scotland would be flush with oil and would not need English aid

* On its own, Scotland could pursue the kind of policies that have given Ireland a booming economy

* Independence and economic growth would draw thousands of talented ex-pat Scots back to the land of their forebears

No...

* Scotland receives more from the UK government than it pays in tax and would be worse off without English subsidies

* Most Scots want devolution, but have never wanted to leave the UK

* If the UK broke up, the English and Scots alike would see their influence in the world diminish