The Scottish Government’s latest Government Expenditure and Revenue Scotland (GERS) will be reported today. 

The figures detail the difference between what Scotland raises in taxes and the amount spent on public services. 

Each year, the numbers add fuel to the constitutional debate – with one side claiming they expose the financial problems which would beset independence, and the other saying they underline the costs of staying in the Union.  

But what do they actually tell us? And what are the pros and cons of using the figures to inform debates about Scotland’s future?  

What’s the background to the Gers figures?   

GERS figures were first published in 1992 under the UK prime minister at the time, John Major.  

At the time, Conservative ministers in the Scottish Office believed the figures would work against the case for devolution by showing how much Scotland received from the Treasury compared to how much it put in.  

In 1999 they began to be produced by the Scottish Government, and by 2014 were described as “the authoritative publication on Scotland’s public finances”in the independence white paper.   

READ MORE: GERS report set to show North Sea boost to 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.  

The Scottish Government’s website says the main aim of GERS is to “enhance public understanding of fiscal issues in Scotland”.

The Herald:   

Who produces the report?  

GERS is a National Statistics publication, which means that it is independently assessed and produced away from any political influence or interference.  

This means it comes direct from the desks of the Civil Service, and is not passed through Minsterial hands or those of their spin doctors.  

Do they tell anything the finances of an independent Scotland? 
No. The GERS figures only relate to the economics of Scotland in the Union, its strengths and weaknesses as part of the K. 

Economists have said they are a “useful starting point”, but that’s about it. This hasn’t stopped them frombeing used in the past by both pro-independence and pro-Union voters to make their cases.  

How are GERS calculated? 

The difficulty with GERS is the way they are compiled. Spending is not estimated, but it does contain a proportion of UK spending in Scotland. This final figures is opaque.

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

READ MORE: 'GERS does not give a picture of life after independence'

It also takes into account UK Government spending in non-devolved areas in Scotland including defence, as well as allocating a proportion of the UK's debt interest payments to Scotland.  

The Herald:

When it comes to revenue, there have been complaints that the data used is not collected for Scotland and has to be estimated from UK figures.  

However, 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.  

Other revenues - particularly those gathered by HMRC - need estimation.  

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