This article appears as part of the Unspun: Scottish Politics newsletter.

Are you ready for a test? Michelle Thomson, the former RBS analyst who is now an SNP MSP on Holyrood’s finance committee, has one you can try. 

The Thomson Test is simple. It boils down to this: Are you a realist or a muppet? 

Green co-leader and minister Lorna Slater took it on Tuesday. 

Let’s just say she didn’t win a realist’s badge.

One of the finance committee’s key jobs is to scrutinise the arithmetic behind new legislation, the financial memoranda that accompany all Scottish Parliament Bills. 

These forecast costs and savings, showing how various burdens and benefits apply to the Scottish Government, councils, public bodies and you and me. 

Because the financial memorandum (FM) of a Bill always looks to the future, the numbers are necessarily best estimates rather than precise data.

But that doesn’t let the government or an MSP with a private bill off the hook. 

The numbers must be rooted in evidence and experience, not plucked from the air or the idealised imaginings of an otherworldly bureaucracy.

The committee is particularly allergic to figures presented as a wide range. 

Last year, for example, it shredded the FM for the Government's National Care Service Bill that put the cost at between £644 million and £1.26bn by 2026/27.

In other words, it could cost one figure, or it could be twice that. Useless or what?

The government has since delayed the Bill to revise its numbers.

Ms Thomson is currently applying her test to the FM for the government’s Circular Economy Bill, which Ms Slater is taking through parliament.

This aims to boost recycling and reduce littering with a mix of carrots and sticks, including better local waste services, fines for litter-bugs and a disposable drinks cup levy.

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The FM says councils could raise £40,000 a year by fining people who throw litter from cars at £80 a pop. It assumes all 500 people fined this way will pay every penny.

Last month, councils said that wasn’t realistic, as only 10-15% of litter fines are paid.

West Lothian’s Jim Jack told the committee those most likely to be fined were least likely to comply. “To be blunt, they face the dilemma of whether to pay fines or pay their rent.”

After hearing that evidence and more on uncertainty in the bill, Ms Thomson posed her test. 

On a scale of zero to ten, how much confidence did councils have in the bill’s estimates? 

South Lanarkshire said four, West Lothian five, and Dundee was “slightly more optimistic”.

On Tuesday, the same question was put to Ms Slater. She said ten out of ten.

An incredulous Ms Thomson said that concerned her “greatly”. 

For one thing, the legislation is an enabling bill. 

It creates a framework for action which is then filled in later through secondary legislation, with those costs highly uncertain.

That alone meant Ms Slater was being over-confident, as by definition the numbers in the FM “can’t be very accurate at all”.

The Herald: SNP MSP Michelle Thomson challenged Green minister Lorna Slater on her grasp of the circular economySNP MSP Michelle Thomson challenged Green minister Lorna Slater on her grasp of the circular economy (Image: Newsquest)
Frankly, the committee had “no clue” what the final cost of the legislation would be, Ms Thomson said, implying Ms Slater had no business saying otherwise. 

The minister defended the figures as the best available at a “strategic level”.

However, as money is spent and raised at ground level, that didn’t impress.

It was an entertaining spat, but did it amount to much? After all, the sums involved, at least in relation to fines, were very small in public finance terms. 

Yes, it did. Because there was a lot more going on below the surface.

The Scottish Government is falling into bad habits just as it faces a budget crisis.  

It has spent hundreds of millions giving public sector workers a pay rise and announced a costly council tax freeze without knowing how to pay for them.

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It risks spending beyond its means. On Monday, the finance committee reported witheringly that “affordability does not appear to be a key factor in… decision-making”. 

The government is also producing more framework bills like the Circularity Economy one which are vague on cost and duck parliamentary scrutiny by omitting the fine print. 

The finance committee is getting sick of it. It wants rigour. It wants details. It wants ministers to stop getting giddy over policy wheezes and focus on the numbers. 

It is putting the government on notice – give us credible figures or get scorched.

Ms Slater failed the Thomson Test this week, but she won’t be the last minister to take it.