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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Commons Confidential: Dave's picnic with Dacre

Revenge is a dish best served cold from a wicker hamper.

Sulking David Cameron can’t forgive the Daily Mail editor, Paul Dacre, for his role in his downfall. The unrelenting hostility of the self-appointed voice of Middle England to the Remain cause felt pivotal to the defeat. So, what a glorious coincidence it was that they found themselves picnicking a couple of motors apart before England beat Scotland at Twickenham. My snout recalled Cameron studiously peering in the opposite direction. On Dacre’s face was the smile of an assassin. Revenge is a dish best served cold from a wicker hamper.

The good news is that since Jeremy Corbyn let Theresa May off the Budget hook at Prime Minister’s Questions, most of his MPs no longer hate him. The bad news is that many now openly express their pity. It is whispered that Corbyn’s office made it clear that he didn’t wish to sit next to Tony Blair at the unveiling of the Iraq and Afghanistan war memorial in London. His desire for distance was probably reciprocated, as Comrade Corbyn wanted Brigadier Blair to be charged with war crimes. Fighting old battles is easier than beating the Tories.

Brexit is a ticket to travel. The Independent Parliamentary Standards Authority is lifting its three-trip cap on funded journeys to Europe for MPs. The idea of paying for as many cross-Channel visits as a politician can enjoy reminds me of Denis MacShane. Under the old limits, he ended up in the clink for fiddling accounts to fund his Continental missionary work. If the new rule was applied retrospectively, perhaps the former Labour minister should be entitled to get his seat back and compensation?

The word in Ukip is that Paul Nuttall, OBE VC KG – the ridiculed former Premier League professional footballer and England 1966 World Cup winner – has cold feet after his Stoke mauling about standing in a by-election in Leigh (assuming that Andy Burnham is elected mayor of Greater Manchester in May). The electorate already knows his Walter Mitty act too well.

A senior Labour MP, who demanded anonymity, revealed that she had received a letter after Leicester’s Keith Vaz paid men to entertain him. Vaz had posed as Jim the washing machine man. Why, asked the complainant, wasn’t this second job listed in the register of members’ interests? She’s avoiding writing a reply.

Years ago, this column unearthed and ridiculed the early journalism of George Osborne, who must be the least qualified newspaper editor in history. The cabinet lackey Ben “Selwyn” Gummer’s feeble intervention in the Osborne debate has put him on our radar. We are now watching him and will be reporting back. My snouts are already unearthing interesting information.

Kevin Maguire is the associate editor (politics) of the Daily Mirror

Kevin Maguire is Associate Editor (Politics) on the Daily Mirror and author of our Commons Confidential column on the high politics and low life in Westminster. An award-winning journalist, he is in frequent demand on television and radio and co-authored a book on great parliamentary scandals. He was formerly Chief Reporter on the Guardian and Labour Correspondent on the Daily Telegraph.

This article first appeared in the 23 March 2017 issue of the New Statesman, Trump's permanent revolution