What is Gers and how is it calculated?

The Scottish government's latest Government Expenditure and Revenue Scotland (Gers) report has been published.

The annual report estimates the difference between what Scotland raises in taxation and what is spent on its public services.

It said the gap fell from £23.7bn to £19.1bn last year, largely due to higher oil and gas revenues.

The deficit represents 9.0% of Scotland's GDP - higher than the 5.2% for the UK as a whole.

The Gers figures were first published in 1992 under UK Prime Minister John Major.

Conservative ministers in the UK government's Scottish Office thought it would help inform the debate on devolution - or would at least help them make the case against the establishment of a Scottish Parliament.

Oil prices were low at the time and they thought the numbers would show how much more Scotland gained from the UK Treasury than it sent south in tax revenues.

Since devolution in 1999, the figures have been compiled by the Scottish government but there is still an annual battle to interpret the numbers from either side in the independence debate.

At the time of the independence referendum in 2014, the Scottish government's White Paper described Gers as "the authoritative publication on Scotland's public finances".

The SNP's Growth Commission blueprint for the finances of an independent Scotland also accepted the Gers figures as its starting point.

Meanwhile, opponents of independence have used the figures to point to a "Union dividend" - arguing that Scotland can only afford its relatively high levels of public spending because it is part of the UK.

No. The Gers figures are not meant to be anything other than a way of showing the current position under the present arrangements.

Economists at the respected Fraser of Allander Institute say that Gers "presents a useful starting point for a discussion regarding the challenges and opportunities that Scotland would face".

And BBC Scotland's economics editor Douglas Fraser says: "One way of looking at them is to measure how big Scotland's deficit would be, if the country were to have been both independent and if its public finances were performing exactly as they did within the UK.

"It would probably perform rather differently if Holyrood pulled the tax, spending and borrowing levers in different ways to the Treasury in London.

"It could have pulled those levers in a smarter way, or left a bigger deficit.

"Everything around this is contested. But what can be said is that this helps illustrate the health or weakness of Scottish public finances."

The Fraser of Allander Institute has tried to explain how Gers is compiled by Scottish government statisticians.

It points out that data on the spending side of the equation is not estimated, but some UK spending is allocated to Scotland on a proportional basis.

The total spend is made up of Scottish and local government services and UK welfare spending and pensions in Scotland.

It also includes UK government spending in non-devolved areas in Scotland such as defence, and allocates a proportion of the UK's debt interest payments to Scotland.

For revenues, there have been complaints that the data used is not collected for Scotland and has to be estimated from UK figures.

This has been less of an issue in recent years, with Scottish income tax, council tax, business rates, the profits made by Scottish Water, landfill tax, land and building transactions tax and local authority user charges and fees included.

There are other revenues - particularly those collected by HMRC - where estimation is needed.

The Fraser of Allander Institute says "estimates are not unusual in economic statistics".

And the Scottish government says that Gers is "produced independently of Scottish ministers and has been assessed by the UK Statistics Authority as being produced in line with the Code of Practice for Official Statistics.

"This means the statistics have been found to meet user needs, to be methodologically sound, explained well and produced free of political interference."

The Scottish government has published answers to a list of frequently asked questions about its Gers figures here.

One of the problems with the Gers figures has been that there were no other official regional breakdowns to compare to Scotland's, so the comparison had to be made to the UK as a whole.

But that has recently changed with the ONS publishing regional breakdowns which showed that, outside of London, and the east and southeast of England, most parts of the UK are estimated to raise less revenue than is spent on their behalf.

It has long been the case that Scotland has received more money to deliver services such as health, education and economic development because of the geographical challenges it faces in these areas.

Scotland also has a slightly higher number of people entitled to benefits associated with issues such as long-term ill health.

The national lockdowns prompted by the Covid-19 pandemic required a massive increase in public spending on relief programmes like the furlough scheme and payments to mothballed businesses.

They also caused a drop in tax revenues, throwing the books even further out of balance.

So the 2021 Gers figures reflected both a huge rise in spending and a cut in tax revenue - and thus a large increase in the notional deficit.

The ONS estimated that the UK's public sector net borrowing (or deficit) for the year was £298bn - which is 14.2% of UK GDP (Gross Domestic Product), the highest figure by far since World War Two.

In comparison, Scotland's deficit stood at 22.4% of GDP.