ONS reports that ONS actually quite good at estimating GDP

Estimates rarely change that much, but have got worse since the crash.

A new study by the ONS (pdf) on the practice of revising quarterly GDP reveals that, despite some high-profile revisions, they are actually doing pretty well.

The current practice for GDP figures is to release a preliminary estimate 25 days after the quarter ends, then update it for a second estimate a month later, and release a final estimate shortly before the next quarter ends – before starting the whole process again. Even after the "final" estimate is made, there's the possibility of still more releases:

As further data become available there are potential revisions to the quarterly GDP figures in subsequent QNA releases, as well as in the annual national accounts Blue Book publication.

The Blue Book process enables annual data to be balanced at a much more detailed level and is also the opportunity for major methodological changes to be introduced.

Whenever the preliminary estimate delivers surprising news – as it did with the most recent results – there is always a rush to point out that these estimates are usually revised (as indeed they are). But the overall picture remains remarkably accurate. The following chart compares the GDP growth given in the initial estimate to the final estimate given five years later.

 

There are some pretty large changes month-to-month, but only one revision in the last 20 years which changed the big picture in any substantial way (the near-collapse in growth in early 1998 actually appears not to have occurred).

Even when the whole period is covered, the authors conclude:

In broad terms the picture of growth in GDP over the period from 1961 to 2012 quarter two is similar, irrespective of the maturity of data, although there are some exceptions. In particular the differences caused by revisions in the late 1980s were previously discussed in Brown et al, where a period of consistent upward revisions led to the Pickford Review (1989). The review implemented a number of methodological changes including the publication of a single measure of GDP.

But what about the most recent period of recession and recovery?Has the ONS got worse at making those initial estimates due to the changed economic circumstances?

Maybe.

The below chart shows the absolute revisions to GDP estimates in the first two years. The Pickford review of 1989, which changed the methodology substantially, clearly worked, reducing the mean revision from a change of at least 0.5 points to one of barely 0.2 points. But while there was a period of unprecedented accuracy in the late 1990s and early 2000s, things have got marginally worse recently – even while staying significantly better than they had been two decades before.

 

As a result, the review concludes that:

There is some evidence that in the latest periods, the size of revision has increased [although not significantly]. . .

It is possible that the assumptions and methods underpinning the early estimates of GDP may not be as robust in periods of greater volatility or at turning points in the economy as they were during the long period of stability from 1992 to 2007.

The most important thing to note, however, is that there is no significant trend for the direction of the revision. Although it's usually positive, it hasn't been recently:

 

So if you are hoping that a GDP estimate will be revised, be careful what you wish for – it may not go the way you hope.

GDP percentage growth, quarter on same quarter 1 year ago - estimates.

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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Former Irish premier John Bruton on Brexit: "Britain should pay for our border checks"

The former Taoiseach says Brexit has been interpreted as "a profoundly unfriendly act"

At Kapıkule, on the Turkish border with Bulgaria, the queue of lorries awaiting clearance to enter European Union territory can extend as long as 17km. Despite Turkey’s customs union for goods with the bloc, hauliers can spend up to 30 hours clearing a series of demanding administrative hoops. This is the nightmare keeping former Irish premier John Bruton up at night. Only this time, it's the post-Brexit border between Northern Ireland and the Republic, and it's much, much worse.   

Bruton (pictured below), Taoiseach between 1994 and 1997, is an ardent pro-European and was historically so sympathetic to Britain that, while in office, he was pilloried as "John Unionist" by his rivals. But he believes, should she continue her push for a hard Brexit, that Theresa May's promise for a “seamless, frictionless border” is unattainable. 

"A good example of the sort of thing that might arise is what’s happening on the Turkish-Bulgarian border," the former leader of Ireland's centre-right Fine Gael party told me. “The situation would be more severe in Ireland, because the UK proposes to leave the customs union as well."

The outlook for Ireland looks grim – and a world away from the dynamism of the Celtic Tiger days Bruton’s coalition government helped usher in. “There will be all sorts of problems," he said. "Separate permits for truck drivers operating across two jurisdictions, people having to pay for the right to use foreign roads, and a whole range of other issues.” 

Last week, an anti-Brexit protest on the border in Killeen, County Louth, saw mock customs checks bring traffic to a near standstill. But, so far, the discussion around what the future looks like for the 260 border crossings has focused predominantly on its potential effects on Ulster’s fragile peace. Last week Bruton’s successor as Taoiseach, Bertie Ahern, warned “any sort of physical border” would be “bad for the peace process”. 

Bruton does not disagree, and is concerned by what the UK’s withdrawal from the European Convention on Human Rights might mean for the Good Friday Agreement. But he believes the preoccupation with the legacy of violence has distracted British policymakers from the potentially devastating economic impact of Brexit. “I don’t believe that any serious thought was given to the wider impact on the economy of the two islands as a whole," he said. 

The collapse in the pound has already hit Irish exporters, for whom British sales are worth £15bn. Businesses that work across the border could yet face the crippling expense of duplicating their operations after the UK leaves the customs union and single market. This, he says, will “radically disturb” Ireland’s agriculture and food-processing industries – 55 per cent of whose products are sold to the UK. A transitional deal will "anaesthetise" people to the real impact, he says, but when it comes, it will be a more seismic change than many in London are expecting. He even believes it would be “logical” for the UK to cover the Irish government’s costs as it builds new infrastructure and employs new customs officials to deal with the new reality.

Despite his past support for Britain, the government's push for a hard Brexit has clearly tested Bruton's patience. “We’re attempting to unravel more than 40 years of joint work, joint rule-making, to create the largest multinational market in the world," he said. It is not just Bruton who is frustrated. The British decision to "tear that up", he said, "is regarded, particularly by people in Ireland, as a profoundly unfriendly act towards neighbours".

Nor does he think Leave campaigners, among them the former Northern Ireland secretary Theresa Villiers, gave due attention to the issue during the campaign. “The assurances that were given were of the nature of: ‘Well, it’ll be alright on the night!’," he said. "As if the Brexit advocates were in a position to give any assurances on that point.” 

Indeed, some of the more blimpish elements of the British right believe Ireland, wedded to its low corporate tax rates and east-west trade, would sooner follow its neighbour out of the EU than endure the disruption. Recent polling shows they are likely mistaken: some 80 per cent of Irish voters say they would vote to remain in an EU referendum.

Irexit remains a fringe cause and Bruton believes, post-Brexit, Dublin will have no choice but to align itself more closely with the EU27. “The UK is walking away,” he said. “This shift has been imposed upon us by our neighbour. Ireland will have to do the best it can: any EU without Britain is a more difficult EU for Ireland.” 

May, he says, has exacerbated those difficulties. Her appointment of her ally James Brokenshire as secretary of state for Northern Ireland was interpreted as a sign she understood the role’s strategic importance. But Bruton doubts Ireland has figured much in her biggest decisions on Brexit: “I don’t think serious thought was given to this before her conference speech, which insisted on immigration controls and on no jurisdiction for the European Court of Justice. Those two decisions essentially removed the possibility for Ireland and Britain to work together as part of the EEA or customs union – and were not even necessitated by the referendum decision.”

There are several avenues for Britain if it wants to avert the “voluntary injury” it looks set to inflict to Ireland’s economy and its own. One, which Bruton concedes is unlikely, is staying in the single market. He dismisses as “fanciful” the suggestions that Northern Ireland alone could negotiate European Economic Area membership, while a poll on Irish reunification is "only marginally" more likely. 

The other is a variation on the Remoaners’ favourite - a second referendum should Britain look set to crash out on World Trade Organisation terms without a satisfactory deal. “I don’t think a second referendum is going to be accepted by anybody at this stage. It is going to take a number of years,” he said. “I would like to see the negotiation proceed and for the European Union to keep the option of UK membership on 2015 terms on the table. It would be the best available alternative to an agreed outcome.” 

As things stand, however, Bruton is unambiguous. Brexit means the Northern Irish border will change for the worse. “That’s just inherent in the decision the UK electorate was invited to take, and took – or rather, the UK government took in interpreting the referendum.”