ONS decides to continue with inaccurate RPI calculation

Statistics agency chooses consistency over accuracy.

Against expectations and the recommendations of a number of influential economists, as well as its own consumer prices advisory committee, the ONS has decided not to change how the RPI – one of the two key indices measuring the rate of price inflation – is calculated.

The pressure to examine the index comes from the longstanding difference between the RPI and CPI measures of inflation. Except for the brief period in the midst of the recession, when both indices were recording deflation, RPI has consistently shown levels of inflation higher than CPI. Here's the chart for the last three years, for instance:


Some of that difference is due to the fact that the two indices measure subtly different things – RPI includes a broader measure of housing costs, for instance, and it ignores very high and low income households. But the ONS has known for a while that there is also a discrepancy caused by the different formulae used to calculate them.

The ONS began a consultation into whether and how it should eliminate this "formula effect", and has concluded that:

Use of the arithmetic formulation (known as the ‘Carli’ index formula) in the RPI is the primary source of the formula effect difference between the RPI and the CPI… This formulation does not meet current international standards.

So what's it going to do about it? Well, nothing:

The National Statistician also noted that there is significant value to users in maintaining the continuity of the existing RPI’s long time series without major change, so that it may continue to be used for long-term indexation and for index-linked gilts and bonds in accordance with user expectations.

Therefore, while the arithmetic formulation would not be chosen were ONS constructing a new price index, the National Statistician recommended that the formulae used at the elementary aggregate level in the RPI should remain unchanged.

The ONS will, however, develop a new measure of inflation, called RPIJ, which will use a different, better, mathematical formula.

The consumer prices advisory committee, a body which meets around five times a year to advise the ONS on measures of inflation, accepted that the ONS has a responsibility to make sure that there is a level of continuity in the RPI calculations which would be destroyed if there were a change to the formula. But, given the ONS also has a responsibility to compile those statistics "in line with best practice", CPAC concluded that not changing RPI would be "unsuitable".

On the other side, arguing for no change, were 332 of the 406 replies to the public consultation. The ONS said:

The large majority of responses did not address methodological issues but identified the impact that the changes implied… would have for them.

The competing requirements present a tricky path for the ONS to follow, but it does feel like it has picked the wrong option at this point. The job of the statistics agency is surely to produce accurate statistics, rather than statistics which are continually inaccurate in known ways. The fact that RPI is used to decide the value of, amongst other things, index-linked bonds is a reason for it to be correct, not for it to be artificially inflated.

As it stands, the ONS has decided to continue publishing a "measure" of inflation which has an accepted and understood upward bias of 1 per cent a year. It has done this, not because of any real statistical reasoning, but because greater accuracy would be bad for a majority of stakeholders. That seems like a bizarre abdication of its duty.

Photograph: Getty Images

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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How the shadow cabinet forced Jeremy Corbyn not to change Labour policy on Syria air strikes

Frontbenchers made it clear that they "would not leave the room" until the leader backed down. 

Jeremy Corbyn had been forced to back down once before the start of today's shadow cabinet meeting on Syria, offering Labour MPs a free vote on air strikes against Isis. By the end of the two-hour gathering, he had backed down twice.

At the start of the meeting, Corbyn's office briefed the Guardian that while a free would be held, party policy would be changed to oppose military action - an attempt to claim partial victory. But shadow cabinet members, led by Andy Burnham, argued that this was "unacceptable" and an attempt to divide MPs from members. Burnham, who is not persuaded by the case for air strikes, warned that colleagues who voted against the party's proposed position would become targets for abuse, undermining the principle of a free vote.

Jon Ashworth, the shadow minister without portfolio and NEC member, said that Labour's policy remained the motion passed by this year's conference, which was open to competing interpretations (though most believe the tests it set for military action have been met). Party policy could not be changed without going through a similarly formal process, he argued. In advance of the meeting, Labour released a poll of members (based on an "initial sample" of 1,900) showing that 75 per cent opposed intervention. 

When Corbyn's team suggested that the issue be resolved after the meeting, those present made it clear that they "would not leave the room" until the Labour leader had backed down. By the end, only Corbyn ally Diane Abbott argued that party policy should be changed to oppose military action. John McDonnell, who has long argued for a free vote, took a more "conciliatory" approach, I'm told. It was when Hilary Benn said that he would be prepared to speak from the backbenches in the Syria debate, in order to avoid opposing party policy, that Corbyn realised he would have to give way. The Labour leader and the shadow foreign secretary will now advocate opposing positions from the frontbench when MPs meet, with Corbyn opening and Benn closing. 

The meeting had begun with members, including some who reject military action, complaining about the "discorteous" and "deplorable" manner in which the issue had been handled. As I reported last week, there was outrage when Corbyn wrote to MPs opposing air strikes without first informing the shadow cabinet (I'm told that my account of that meeting was also raised). There was anger today when, at 2:07pm, seven minutes after the meeting began, some members received an update on their phones from the Guardian revealing that a free vote would be held but that party policy would be changed to oppose military action. This "farcical moment", in the words of one present (Corbyn is said to have been unaware of the briefing), only hardened shadow cabinet members' resolve to force their leader to back down - and he did. 

In a statement released following the meeting, a Corbyn spokesperson confirmed that a free vote would be held but made no reference to party policy: 

"Today's Shadow Cabinet agreed to back Jeremy Corbyn's recommendation of a free vote on the Government's proposal to authorise UK bombing in Syria.   

"The Shadow Cabinet decided to support the call for David Cameron to step back from the rush to war and hold a full two day debate in the House of Commons on such a crucial national decision.  

"Shadow Cabinet members agreed to call David Cameron to account on the unanswered questions raised by his case for bombing: including how it would accelerate a negotiated settlement of the Syrian civil war; what ground troops would take territory evacuated by ISIS; military co-ordination and strategy; the refugee crisis and the imperative to cut-off of supplies to ISIS."

George Eaton is political editor of the New Statesman.