Our own fiscal council, the OBR, is very restricted in what it is allowed to say by the party that created it. As a consequence, it is absolutely essential that we have widely respected bodies, principally the IFS but I would also include the Resolution Foundation and the National Institute (NIESR), that are able to provide good quality economic advice at all times, but particularly before General Elections.
A good example is the Conservative manifesto published last Sunday. Without the IFS, it is quite possible that it would have made extravagant promises on public expenditure and it would have also included some tax cuts. But because the media treats the IFS as authoritative and impartial, this year they will have judged that the political costs of a manifesto like that exceeded the benefits.
So the IFS or something like it is essential. But that does not, of course, mean that it is beyond criticism. Indeed it is essential that such criticisms are made (no one is perfect). There are two types of criticism. The first are specific criticisms: it got this piece of analysis or this particular statement wrong. The second is generic: it is often wrong because of a general failing of some kind. Let me take each in turn
A specific criticism I would make is that Paul Johnson’s initial reaction to Labour’s manifesto was ill-judged in the language he used. He used three words that you will not find in the IFS’s written assessment: colossal and not credible. On ‘colossal’, the written text uses the more neutral words ‘very substantial’. More seriously, he said claims that all the tax would be raised from companies and those earning over £80,000 were not credible.
That gave the media an easy headline. For example The Times wrote “Jeremy Corbyn’s plans to raise a “colossal” £83billion in extra taxes to fund an unprecedented public spending spree are “simply not credible”, the Institute for Fiscal Studies has warned.” The Mail wrote “Jeremy Corbyn's hard-Left spending splurge is 'simply not credible': IFS ridicules Labour leader's claim he can raise £83BILLION in extra tax to fund 'colossal' giveaways JUST from the rich - warning EVERYONE will have to pay”. The Guardian wrote “The Institute for Fiscal Studies, the non-partisan tax and spending thinktank, said that it does not believe Labour’s claim that it will be able to achieve everything it plans with 95% of taxpayers not having to pay any extra in tax”