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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MP after a moonlighting job? I've got the perfect opportunity

If it's really about staying in touch with the real world, how about something menial and underpaid? Or reforming parliamentary rules on second jobs...

There she stood outside Number 10 on 13 July last year, the new Prime Minister pledging with earnest sincerity her mission to fight injustice and inequality, to “make Britain a country that works not for a privileged few, but for every one of us”.

 “When it comes to opportunity,” she promised the ‘just managing’ millions, “we won’t entrench the advantages of the fortunate few". Another new day had dawned

But predictably since then it’s been business as usual. If we needed proof, George Osborne has provided it: those who have so little must continue to go without so that the man with so much can have it all.

What would it take for Tory backbenchers to trouble Theresa May’s serenity? Not her u-turn on Brexit. Nor her denial of Parliament’s right to scrutinise the terms of the UK's uncertain future. Certainly not a rampant Labour opposition.

But were she to suggest that they give up their adventures in the black economy and focus on the job their constituents pay them for, she would face a revolt too bloody to contemplate.

Fifteen years ago, I introduced the short-lived Members of Parliament (Employment Disqualification) Bill. My argument was simply that being an MP is a full-time job for which MPs are paid a full-time salary. If they can find time to augment an income already three times the national average, they can’t be taking it seriously or doing it properly.

Imagine the scandal if other public servants - teachers perhaps or firefighters – were to clock off whenever they fancied to attend to their nice little earners on the side. What would become of Britain’s economy if employers were unable to prevent their workers from taking home full pay packets but turning up to work only when they felt inclined?

But that’s what happens in the House of Commons. Back in 2002, my research showed that a quarter of MPs, most of them Conservatives, were in the boardroom or the courtroom or pursuing lucrative consultancies when they should have been serving their communities. And it was clear that their extra-curricular activities were keeping them from their Parliamentary duties. For example, in the six month period I analysed, MPs with paid outside interests participated on average in only 65 per cent of Commons votes while MPs without second jobs took part in 91 per cent.

I doubt that much has changed since then. If anything, it’s likely that the proportion of moonlighting Members has risen as the number of Tory MPs has increased with successive elections.

Their defence has always been that outside interests make for better politicians, more in touch with the "real world". That’s entirely bogus. Listening to people in their surgeries or in their local schools, hospitals and workplaces provides all the insight and inspiration a conscientious MP could need. The argument would be stronger were absentee MPs supplementing their experience and income in the menial, insecure and underpaid jobs so many of their constituents are forced to do. But, they aren’t: they’re only where the money is.

It’s always been this way. The Parliamentary timetable was designed centuries ago to allow MPs to pursue a gentleman’s interests. Until relatively recently, the Commons never sat until after noon so that its Members could attend their board meetings – or edit the Evening Standard - and enjoy a good lunch before legislating. The long summer recess allowed them to make the most of the season, indulge in a few country sports and oversee the harvest on their estates.

The world has changed since Parliamentary precedent was established and so has the now overwhelming workload of a diligent MP. There are many of them in all parties. But there are also still plenty like George Osborne whose enduring sense of entitlement encourages them to treat Parliament as a hobby or an inheritance and their duty to their constituents as only a minor obstacle to its enjoyment.

Thanks to Osborne’s arrogance, the Committee on Standards in Public Life now has the unflunkable opportunity to insist on significant, modernising reforms which remind both MPs and their electors that public service should always take precedence over private interest. And if sitting MPs can’t accept that principle or subsist on their current salary, they must make way for those who can. Parliament and their constituents would be better off without them.

Peter Bradley was the Labour MP for The Wrekin between 1997 and 2005.