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.

Photo: Getty
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If the left leaves it to David Cameron, we'll have Brexit for sure

Only an upbeat, leftwing case can keep Britain in the European Union.

After months flapping and hesitation, and with much of the reporting and detail so dull that it has barely penetrated the consciousness of even those who speak the language of ‘directives’ and treaty provisions, the EU referendum is upon us. With David Cameron signalling concrete outcomes for negotiations, we seem to be set for June, whatever the protests from opposition parties about the date being too close to local and national elections.  

Cameron’s deal, whose most substantive element consists of denying in-work benefits to European citizens, exemplifies the kind of debate that Conservative strategists want to create: a tedious, labyrinthine parochialism, blending the EU’s procedural dullness with an unquestioned mythology of the little Englander. Try actually reading the various letters, let alone the draft decisions, that Cameron extracted from Donald Tusk, and the agreement turns to putty in your head. But in summary, what Cameron is negotiating is designed to keep the EU debate as an in-house affair within the right, to continue and formalise the framing of the debate as between two strains of anti-migrant sentiment, both of them backed by big business.

The deal may be reactionary, but it is also mediocre in its scope and impact. The worries that many of us had in the leftwing pro-In camp, that Cameron’s deal would push back freedom of movement and working and environmental protections so far that we would be unable to mobilise for continued membership of the EU, can now be put to bed. Quite the opposite of allowing Cameron's narrative to demoralise us, the left must now seize an opportunity to put imagination and ideas back at the heart of the referendum debate.

The British political landscape in which that debate will play out is a deceptively volatile environment. Party allegiance is at a nearly all time low. Inequality is growing, and so is the gap between attitudes. The backbone of the UKIP vote – and much of the Out vote – will come from a demographic that, sometimes impoverished by the legacy of Thatcherite economic policy, sees itself as left behind by migration and change. On top of the class war, there is a kind of culture war underway in today’s Britain: on one side those who see LGBT rights, open borders and internationalism as the future; on the other side, those who are scared of the future. About the only thing these groups have in common with one another is their anti-establishment instincts, their total disdain and mistrust of politics as usual.

The only political movement to have broken through the fog of cynicism and disillusionment in British politics has come from the left. Jeremy Corbyn’s rise to the leadership of the Labour has unleashed something new - and while large parts of the press, and some Labour backbenchers, have portrayed this rise as a crusade of the “croissant eating” metropolitan elite, the reality is very different. The rise of the new Labour left has given voice to a renewed socialist and working class politics; its explicitly radical, outsider approach has given it traction across the social divides – among the young looking for a future, and among Labour’s old base. 

A politics of hope – however vague that term might sound – is the only real answer to the populist Euroscepticism that the Out campaign will seek to embody. Radical politics, that proposes an alternative narrative to the scapegoating of migrants, has to find voice in the course of this referendum campaign: put simply, we need to persuade a minimum wage worker that they have more in common with a fellow Polish migrant worker than they do with their employer; we need to persuade someone on a social housing waiting list should blame the privatisation of the housing market, not other homeless families. Fundamentally, the real debate to be had is about who the public blames for social injustice: that is a question which only the left can satisfactorily answer.

The outsider-led volatility of British politics gives the EU referendum a special kind of unpredictability. For voters who have lost faith in the political establishment – and who often have little materially to lose from Brexit – the opportunity to deliver a blow to David Cameron this summer will be tempting. The almost consciously boring, business-dominated Britain Stronger In Europe campaign makes a perfect target for disenfranchised public sentiment, its campaigning style less informed by a metropolitan elite than by the landed gentry. Its main weapons – fear, danger and uncertainty – will work on some parts of the electorate, but will backfire on others, much as the Better Together campaign did in the Scottish referendum.

Last night, Another Europe is Possible held a launch meeting of about a hundred people in central London - with the backing of dozens of MPs, campaigners and academics across the country. It will aim to provide a radical, left wing voice to keep Britain in the EU.

If Britain votes to leave the EU in June, it will give the Right a mandate for a renewed set of attacks on workers’ rights, environmental protections, migrants and freedom of movement. But without an injection of idealism and radicalism,  an In vote will be a mandate for the status quo - at home and in Brussels. In order to seize the real potential of the referendum, the left has to approach the campaign with big ideas and demands. And we have to mobilise.