Osborne's dynamic plan

How a technical change in Treasury forecasting could help scrap the 45p tax rate.

At the Treasury Select Committee yesterday, in between being quizzed by MPs angry at the extent of the pre-budget leaks, George Osborne revealed that he was planning to enable the OBR to make greater use of so-called "dynamic scoring" when they prepare their economic forecasts – but only when examining tax plans. It may not sound it, but if he made that change, it would be a huge coup for the right.

Dynamic scoring is the practice of including behavioural changes in economic forecasts. Without it, in a static model, changes to revenue after something like a tax hike are facile to calculate. If VAT at 17.5 per cent takes in (say) £175bn, then VAT at 20 per cent will take in £200bn. Similarly, if you are trying to calculate the effects on government revenues of spending £100m buying new trains for the east coast main line, then you can conclude that it will cost £100m – you buy the new trains, everyone carries on riding the line, and nothing changes.

What a static model says is that people are blind to the effect that government actions have when they are choosing what to do. Clearly, that is untrue. But it is also very easy to calculate, which is why it has stuck around for so long.

Dynamic models include all these changes of behaviour. So when looking at a dynamic model for rail investment, you can take into account the fact that nicer trains will make people more likely to travel, boosting ticket revenue; and when looking at a dynamic model for VAT rises, you bear in mind the fact that as prices rise, people buy fewer things, so that an 11 per cent rise in VAT won't lead to an 11 per cent rise in VAT revenue.

The problem for economists is that dynamic models are a lot harder to calculate. Not only are there far more variables to take into account, but you open yourself up to more avenues of attack from political opponents. The combined effect of all the assumptions you must make means that your conclusions can be deeply flawed if you get too many wrong, and, as the IFS says (pdf), can "[open] the door to large controversies if these guesses are made – or perceived to be made – in a politically biased way." While static models contain assumptions that are obviously false, dynamic models still contain assumptions, which can still be just as false. And unlike static models, we can't know which ones these are until it is too late.

So why does George Osborne want to introduce dynamic scoring into OBR models? Does he believe that the government's economists have uncovered a breakthrough understanding in behavioural responses to government intervention?

A clue can be found in HMRC's report into the 50p tax rate, which found that dropping the rate down to 45p would cost far less than expected, because of expected behavioural changes. Indeed, this sort of dynamic thinking is the cornerstone of the Laffer curve, the economic theory that, past a certain point, increasing tax rates reduces revenues.

What Osborne will be hoping is that allowing the OBR to make its models more dynamic still will strengthen the rationale for scrapping the 45p rate entirely, as well as for cutting corporation tax all the way down to 20p by the end of parliament.

Yet while the OBR will be "informed" by these new dynamic models when it comes to tax policy, they won't be taking account of the same information when examining the justification for government investment, where, far from strengthening Osborne's preferred policy, it would weaken it. If dynamic scoring is indeed implemented in this narrow fashion, Osborne will have scored a stealth victory for future Tory policy.

Money on the mind: A 19th century phrenology chart. Credit: Getty

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

Getty Images.
Show Hide image

Voters are turning against Brexit but the Lib Dems aren't benefiting

Labour's pro-Brexit stance is not preventing it from winning the support of Remainers. Will that change?

More than a year after the UK voted for Brexit, there has been little sign of buyer's remorse. The public, including around a third of Remainers, are largely of the view that the government should "get on with it".

But as real wages are squeezed (owing to the Brexit-linked inflationary spike) there are tentative signs that the mood is changing. In the event of a second referendum, an Opinium/Observer poll found, 47 per cent would vote Remain, compared to 44 per cent for Leave. Support for a repeat vote is also increasing. Forty one per cent of the public now favour a second referendum (with 48 per cent opposed), compared to 33 per cent last December. 

The Liberal Democrats have made halting Brexit their raison d'être. But as public opinion turns, there is no sign they are benefiting. Since the election, Vince Cable's party has yet to exceed single figures in the polls, scoring a lowly 6 per cent in the Opinium survey (down from 7.4 per cent at the election). 

What accounts for this disparity? After their near-extinction in 2015, the Lib Dems remain either toxic or irrelevant to many voters. Labour, by contrast, despite its pro-Brexit stance, has hoovered up Remainers (55 per cent back Jeremy Corbyn's party). 

In some cases, this reflects voters' other priorities. Remainers are prepared to support Labour on account of the party's stances on austerity, housing and education. Corbyn, meanwhile, is a eurosceptic whose internationalism and pro-migration reputation endear him to EU supporters. Other Remainers rewarded Labour MPs who voted against Article 50, rebelling against the leadership's stance. 

But the trend also partly reflects ignorance. By saying little on the subject of Brexit, Corbyn and Labour allowed Remainers to assume the best. Though there is little evidence that voters will abandon Corbyn over his EU stance, the potential exists.

For this reason, the proposal of a new party will continue to recur. By challenging Labour over Brexit, without the toxicity of Lib Dems, it would sharpen the choice before voters. Though it would not win an election, a new party could force Corbyn to soften his stance on Brexit or to offer a second referendum (mirroring Ukip's effect on the Conservatives).

The greatest problem for the project is that it lacks support where it counts: among MPs. For reasons of tribalism and strategy, there is no emergent "Gang of Four" ready to helm a new party. In the absence of a new convulsion, the UK may turn against Brexit without the anti-Brexiteers benefiting. 

George Eaton is political editor of the New Statesman.