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.

Photo: Getty
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Like it or hate it, it doesn't matter: Brexit is happening, and we've got to make a success of it

It's time to stop complaining and start campaigning, says Stella Creasy.

A shortage of Marmite, arguments over exporting jam and angry Belgians. And that’s just this month.  As the Canadian trade deal stalls, and the government decides which cottage industry its will pick next as saviour for the nation, the British people are still no clearer getting an answer to what Brexit actually means. And they are also no clearer as to how they can have a say in how that question is answered.

To date there have been three stages to Brexit. The first was ideological: an ever-rising euroscepticism, rooted in a feeling that the costs the compromises working with others require were not comparable to the benefits. It oozed out, almost unnoticed, from its dormant home deep in the Labour left and the Tory right, stoked by Ukip to devastating effect.

The second stage was the campaign of that referendum itself: a focus on immigration over-riding a wider debate about free trade, and underpinned by the tempting and vague claim that, in an unstable, unfair world, control could be taken back. With any deal dependent on the agreement of twenty eight other countries, it has already proved a hollow victory.

For the last few months, these consequences of these two stages have dominated discussion, generating heat, but not light about what happens next. Neither has anything helped to bring back together those who feel their lives are increasingly at the mercy of a political and economic elite and those who fear Britain is retreating from being a world leader to a back water.

Little wonder the analogy most commonly and easily reached for by commentators has been that of a divorce. They speculate our coming separation from our EU partners is going to be messy, combative and rancorous. Trash talk from some - including those in charge of negotiating -  further feeds this perception. That’s why it is time for all sides to push onto Brexit part three: the practical stage. How and when is it actually going to happen?

A more constructive framework to use than marriage is one of a changing business, rather than a changing relationship. Whatever the solid economic benefits of EU membership, the British people decided the social and democratic costs had become too great. So now we must adapt.

Brexit should be as much about innovating in what we make and create as it is about seeking to renew our trading deals with the world. New products must be sought alongside new markets. This doesn’t have to mean cutting corners or cutting jobs, but it does mean being prepared to learn new skills and invest in helping those in industries that are struggling to make this leap to move on. The UK has an incredible and varied set of services and products to offer the world, but will need to focus on what we do well and uniquely here to thrive. This is easier said than done, but can also offer hope. Specialising and skilling up also means we can resist those who want us to jettison hard-won environmental and social protections as an alternative. 

Most accept such a transition will take time. But what is contested is that it will require openness. However, handing the public a done deal - however well mediated - will do little to address the division within our country. Ensuring the best deal in a way that can garner the public support it needs to work requires strong feedback channels. That is why transparency about the government's plans for Brexit is so important. Of course, a balance needs to be struck with the need to protect negotiating positions, but scrutiny by parliament- and by extension the public- will be vital. With so many differing factors at stake and choices to be made, MPs have to be able and willing to bring their constituents into the discussion not just about what Brexit actually entails, but also what kind of country Britain will be during and after the result - and their role in making it happen. 

Those who want to claim the engagement of parliament and the public undermines the referendum result are still in stages one and two of this debate, looking for someone to blame for past injustices, not building a better future for all. Our Marmite may be safe for the moment, but Brexit can’t remain a love it or hate it phenomenon. It’s time for everyone to get practical.