This Wednesday, more statistics will be piled on top of the already bewildering heap of figures generated by the referendum debate.

On the Unionist side, Better Together will present what it calls the Union Dividend, the amount by which it says each Scottish household benefits from being part of the UK. On the other side, the Nationalists will produce an entirely different set of figures they say prove how much Scots will benefit from independence; they call it the Independence Bonus.

The question is: how much further forward will the estimates take us in a debate that has already shown the extent to which figures can obscure as well as reveal? Over the weekend, for example, there were more claims and counter-claims over the set-up costs of independence. The Treasury said an independent Scotland would have to pay £2.7 billion to set up 180 government departments but the Scottish Government said this was based on a misinterpretation of figures in its White Paper.

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In response, Danny Alexander, the Chief Secretary to the Treasury, has accused the Scottish Government of refusing to reveal how much the set-up charge would be for an independent country, and on this there is some cause for concern for voters who want the facts.

However wildly overstated the Treasury's £2.7bn estimate may be, we know that there would be a cost attached to setting up an independent country and disentangling the Government of Scotland from that of the rest of the UK. Military bases would have to be reorganised; embassies would be required; there would be a new, expanded civil service; and there would have to be a range of new agencies and departments handling foreign affairs, defence, social security and the other business of a new state.

On the other hand, there could be savings to be had from independence, savings the Scottish Government has said would help pay for the set-up costs. One estimate is that £250m would be saved from ditching Trident and another £50m saved from no longer sending MPs to Westminster; it is also true that much of the infrastructure needed for an independent country already exists, although it is unclear how Scotland's share would be calculated and apportioned.

The most important point is that, for the sake of voters, the Scottish Government must put a figure on the cost of setting up the new machinery of government. It has rubbished the Treasury's claims, but the Scottish Government knows that the credibility of its prospectus, and to a large extent the chances of success in the referendum, rests on the question of how much independence will cost and it must do more to explain what the initial cost could be.

There can never be absolute certainty - there are inevitability many ifs, buts and maybes in the establishment of a new state - but Scottish voters are entitled to know the Scottish Government's best estimate of what the set-up costs for an independent Scotland would be and how that estimate has been calculated.