In Budd We Trust
"Trust me, I'm Sir Alan Budd". That, in effect, was the OBR chairman's defence to MPs this morning when grilled on the new body's much vaunted independence.
Sir Alan came out of semi-retirement to head up the new forecasting body and at times today he looked as though he was looking forward to going back to it. He was pressed on why the new forecasting body had revised down the number of job losses expected to result from budget cuts - and later released the numbers, just minutes before what might have been an uncomfortable Prime Minister's Questions.
I went into this in detail last week. Understandably, MPs thought it was all pretty fishy.
In his testimony, Sir Alan admitted that the OBR had perhaps been naive, but he insisted that there had been no political interference in the OBR's work. And if you don't believe him... well, how could you not believe him? He's Sir Alan Budd, a distinguished former Treasury civil servant and MPC member with an unimpeachable reputation.
Minutes before the hearing, he released to the committee a detailed explanation of the forecasts, which, if nothing else, should remind everyone just how complicated this predictions business really is.
With this document we now know that applying these changes to the OBR's "before" forecast for public sector employment would have raised the number of jobs expected under Labour's policies by 140,000 by 2014-15. That means that the "after" figure - the number of forecast job losses which are directly attributable to decisions in the Budget - is not 30,000 but 160,000 by 2014-15.
The paper also makes clear that David Cameron was wrong to say that the coalition's policies would lead to fewer job losses over the next two years than under Labour - he was comparing two very different numbers.
Sir Alan did not criticise Mr Cameron for doing this at the time and he didn't take the opportunity to do so today. He did admit that there should have been a stronger health warning on the 30 June release, explaining clearly that the two sets of numbers could not be compared.
It is strange that there weren't any. After all, there were plenty of health warnings in the Budget explaining why differences between the pre-Budget and the Budget - like the fall in the growth forecast, to take a rather important example - could not necessarily be considered the result of Mr Osborne's cuts. The official explanation for the lack of detail had been that the release was rushed out, in response to a leak. But Sir Alan told MPs that the document had already been written for release later in the week. They just brought publication forward to respond to the leak.
The OBR note does make clear that it was not making explicit judgements about future policy in changing their forecasting assumptions in the lead up to the Budget. In many cases, they were actually moving away from the subjective judgements about the future which had gone into previous forecasts.
However, it is still possible to argue that at least one change had the effect of anticipating government policy, even if that was not the stated intention.
Previously, officials had used demographic forecasts and estimates of opt-out rates etc to calculate the likely course for public-sector pension spending. In its Budget forecast the OBR replaced all that with a simple assumption that spending will remain constant as a proportion of the pay bill.
You can see that this has the advantage of simplicity. It also had the biggest single impact on the forecast - at a stroke raising the employment forecast for 2014-15 by 120,000.
But there are known and well-understood demographic pressures pushing up public-sector pension costs over the next few years, included in forecasts by the likes of the National Audit Office. Even if this was not the goal, stating that costs will remain constant as a share of the pay bill has the effect of assuming that policy changes will intervene to keep costs on a stable path, when they would otherwise go up.
So much for the detail. I can't speak for the MPs but you have to assume they believe Sir Alan's protestations. How could they not? He's Sir Alan Budd.
And yet, it is not usually a sign of strength for an institution to owe every last shred of its credibility to the personal reputation of the boss.
Sir Alan said that the past few weeks had been "personally very painful indeed." You can see why.
He also said he hoped that the mud would not stick to the OBR as an institution, which he dubbed a "brilliant innovation". But if it is indeed going to be brilliant, it will surely need to have more to fall back on in defending its credibility than the reputation of one single individual.