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.

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I'm far from convinced by Cameron's plans for Syria

The Prime Minister has a plan for when the bombs drop. But what about after?

In the House of Commons today, the Prime Minister set out a powerful case for Britain to join air strikes against Isil in Syria.  Isil, he argued, poses a direct threat to Britain and its people, and Britain should not be in the business of “outsourcing our security to our allies”. And while he conceded that further airstrikes alone would not be sufficient to beat Isil, he made the case for an “Isil first” strategy – attacking Isil now, while continuing to do what we can diplomatically to help secure a lasting settlement for Syria in which Assad (eventually) plays no part.

I agreed with much of David Cameron’s analysis. And no-one should doubt either the murderous barbarism of Isil in the region, or the barbarism they foment and inspire in others across the world.  But at the end of his lengthy Q&A session with MPs, I remained unconvinced that UK involvement in airstrikes in Syria was the right option. Because the case for action has to be a case for action that has a chance of succeeding.  And David Cameron’s case contained neither a plan for winning the war, nor a plan for winning the peace.

The Prime Minister, along with military experts and analysts across the world, concedes that air strikes alone will not defeat Isil, and that (as in Iraq) ground forces are essential if we want to rid Syria of Isil. But what is the plan to assemble these ground forces so necessary for a successful mission?  David Cameron’s answer today was more a hope than a plan. He referred to “70,000 Syrian opposition fighters - principally the Free Syrian Army (FSA) – with whom we can co-ordinate attacks on Isil”.

But it is an illusion to think that these fighters can provide the ground forces needed to complement aerial bombardment of Isil.  Many commentators have begun to doubt whether the FSA continues to exist as a coherent operational entity over the past few months. Coralling the myriad rebel groups into a disciplined force capable of fighting and occupying Isil territory is a heroic ambition, not a plan. And previous efforts to mobilize the rebels against Isil have been utter failures. Last month the Americans abandoned a $500m programme to train and turn 5,400 rebel fighters into a disciplined force to fight Isil. They succeeded in training just 60 fighters. And there have been incidents of American-trained fighters giving some of their US-provided equipment to the Nusra Front, an affiliate of Al Qaeda.

Why has it proven so hard to co-opt rebel forces in the fight against Isil? Because most of the various rebel groups are fighting a war against Assad, not against Isil.  Syria’s civil war is gruesome and complex, but it is fundamentally a Civil War between Assad’s forces and a variety of opponents of Assad’s regime. It would be a mistake for Britain to base a case for military action against Isil on the hope that thousands of disparate rebel forces can be persuaded to change their enemy – especially when the evidence so far is that they won’t.

This is a plan for military action that, at present, looks highly unlikely to succeed.  But what of the plan for peace? David Cameron today argued for the separation of the immediate task at hand - to strike against Isil in Syria – from the longer-term ambition of achieving a settlement in Syria and removing Assad.  But for Isil to be beaten, the two cannot be separated. Because it is only by making progress in developing a credible and internationally-backed plan for a post-Assad Syria that we will persuade Syrian Sunnis that fighting Isil will not end up helping Assad win the Civil War.  If we want not only to rely on rebel Sunnis to provide ground troops against Isil, but also provide stable governance in Isil-occupied areas when the bombing stops, progress on a settlement to Syria’s Civil War is more not less urgent.  Without it, the reluctance of Syrian Sunnis to think that our fight is their fight will undermine the chances of military efforts to beat Isil and bring basic order to the regions they control. 

This points us towards doubling down on the progress that has already been made in Vienna: working with the USA, France, Syria’s neighbours and the Gulf states, as well as Russia and Iran. We need not just a combined approach to ending the conflict, but the prospect of a post-war Syria that offers a place for those whose cooperation we seek to defeat Isil. No doubt this will strike some as insufficient in the face of the horrors perpetrated by Isil. But I fear that if we want not just to take action against Isil but to defeat them and prevent their return, it offers a better chance of succeeding than David Cameron’s proposal today. 

Stewart Wood is a former Shadow Cabinet minister and adviser to Ed Miliband. He tweets as @StewartWood.