Statistic cited to defend austerity partially based on Excel error

How bad did Reinhart and Rogoff get it?

 

Reinhart and Rogoff

It's always hard to work out how much policy is based on actual evidence, rather than the preconceptions of politicians and policymakers, but if any research has had an effect, it's surely Carmen Reinhart and Ken Rogoff's 2009 book This Time it's Different. It's the source of a claim which has outgrown its roots, and come to be cited in policy debates worldwide: that growth drops precipitously if the ratio of debt to GDP rises above 90 per cent. But now, a new paper shows that that claim is partially the result of some astonishing oversight – including an error in the authors' Excel spreadsheet which excluded five countries from the analysis.

The book itself examines the link between the ratio of debt to GDP and growth rates in a raft of countries from World War II onwards. It finds that the higher the debt to GDP ratio, the lower real growth in those countries – and that there is a massive drop of debt to GDP ratios rise above 90 per cent, when the average growth rate becomes slightly negative.

To be fair to Reinhart and Rogoff (or R&R, as the cool kids do not say), the claim they make has been spun out of proportion by supporters keen to use it for political ends. The authors don't explicitly present the 90 per cent level as a cliff, just highlight what the data says; and they don't draw a causal inference, speaking, as they point out today, "of 'association' and not 'causality.'"

Herndon, Ash and Pollin

Even so, however, no other researcher has been able to replicate their "association", and no satisfactory explanation has been given as to why that is. Until now. The new critique, "Does High Public Debt Consistently Stifle Economic Growth? A Critique of Reinhart and Rogoff" by Thomas Herndon, Michael Ash and Robert Pollin (HAP, in economistspeak), is damning. It highlights three inaccuracies in R&R: "coding errors, selective exclusion of available data, and unconventional weighting of summary statistics".

Of those, the first is the most painful, albeit the least important. Reinhart and Rogoff simply added up their spreadsheet wrong. Mike Konczal's report on the paper illustrates the error: the blue box encloses the cells which R&R used to estimate the average; notice how it doesn't go all the way to the bottom? It should:

Missing out the last five rows – particularly Belgium, which had an average growth rate of 2.6 per cent during the years it had a debt to GDP ratio above 90 per cent – changes the average from -0.1 per cent to 0.2 per cent.

That error explains why no-one else could replicate R&R's findings – but the other two problems cast further doubt on whether even the 0.2 per cent figure is acceptable.

The HAP paper finds that R&R exclude certain years in certain countries for no documented reason. These include five years in which New Zealand has a debt to GDP ratio of over 90 per cent. With those years included, the average growth during New Zealand's six years above the threshold is 2.58 per cent; with them excluded it plummets to -7.6 per cent. Similar, albeit smaller, results are found for Australia and Canada, which are also excluded for short periods immediately after the war.

Finally, the HAP paper addresses the way in which R&R weight the results. Each country's data is averaged out, and then the average of those averages is found. That has the effect of valuing the 19 data points that the UK offers above 90 per cent debt/GDP – which average 2.4 per cent growth – with the same weight as the single year that New Zealand offers, when growth was -7.6 per cent.

With all the criticisms applied, the HAP paper reports that the average growth rate for years with a debt/GDP ratio is not -0.1 per cent, but 2.2 per cent. The steep drop-off at 90 per cent disappears; and the credibility of those who cited it should take a hit.

Reinhart and Rogoff Respond

But Reinhart and Rogoff aren't taking it sitting down. With an astonishing turnaround, they have issued a response – published at 3am Boston time – which addresses the critique.

They concede the Excel error – "full stop" – but give a defence for the other two points. The full data for the years excluded was not available when they did their research, they argue, and so while it may make sense to include now, they cannot be held responsible for its absence:

This charge, which permeates through their paper, is one we object to in the strongest terms. The “gaps” are explained by the fact there were still gaps in our public data debt set at the time of this paper.

They also defend the odd choice of weightings, saying that:

Our approach has been followed in many other settings where one does not want to overly weight a small number of countries that may have their own peculiarities.

That is, they argue that just because there is more data for Britain than New Zealand, that does not mean Britain should be weighed more strongly, since that runs the risk that its "peculiarities" might alter the result.

The problem is that neither approach is obviously preferable. While R&R have a point, so to do HAP – which leaves us in the position of questioning the viability of such analysis in the first place.

But R&R make one final defence:

[Herndon et al], too, find lower growth associated with periods when debt is over 90 per cent. Put differently, growth at high debt levels is a little more than half of the growth rate at the lowest levels of debt.

They published this table, via Business Insider, to make the claim clearer:

Does it even matter?

But here's the thing: Reinhart and Rogoff's claim that the HAP paper agrees with them is more evidence of the supreme obviousness of their associative claim. "A high ratio of debt to GDP is correlated with low growth in GDP" is not an interesting finding, it's as close to a mathematical truism as economic statements come. Reinhart and Rogoff's paper is only important insofar as people have read two things into it which aren't true: firstly, that high debt to GDP ratios cause low growth; and secondly, that there is a discontinuity at 90 per cent, where things get much, much worse.

Reinhart and Rogoff themselves disavow the first claim, writing that:

We are very careful in all our papers to speak of "association" and not "causality".

And the second claim has been put to bed by the Herndon et al paper. There is no major drop at 90 per cent, because that was an artefact of incomplete data, errors in coding, and an odd weighting system.

(Incedentally, the 90 per cent discontinuity was a red herring anyway, because it only exists due to the fact that R&R broke up their data into bands 30 percentage points wide. Anyone focusing too heavily on it as a "magic number" simply failed to read the methods section)

And so we are left in much the same place we were beforehand. There remains no evidence that high debt causes GDP growth to slow, rather than slow GDP growth causing high debt. And that lack of evidence will have precisely no effect on public debate, because it's basically all data-free anyway.

There is one change, though. The thesis that Excel is the most dangerous piece software in the world just got a massive boost.

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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The politics of the kiss

From the classical period via the Kremlin to the Clintons: a brief history of political smooching.

Iowa and New Hampshire are behind us. Super Tuesday beckons. For fans of the competitive sport of baby-kissing, this is as good as it gets.

Meanwhile, closer to Britain, kissing’s in our very constitution. Jeremy Corbyn’s future, depending on his success, could involve taking a trip to the Palace to kiss hands as Prime Minister – and as a republican. Being sworn into the Privy Council in November, he even managed a peck on the royal paw, but reportedly stood fast and did not kneel.

Why is there so much snogging in politics? 

Ancient Romans and Persians established – dare we – a pecking order on meeting. This ritual would make it instantly clear if they were equals (full-on, mouthy kiss, the basium), separated by a slight gap (cheeky peck, an osculum), or vast unequals (foot-kissing accompanied by much grovelling). Even heads of state greeted people in this way.

And there was nothing more dramatic – and bizarre – than the socialist fraternal kiss. Kremlinologists would even measure its intensity, to see how close Communist leaders were. The rule was to do three alternate kisses on the cheek, aping the Ancien Régime’s Orthodox Easter greeting. When two leaders were especially chummy – like then Soviet leader Leonid Brezhnev and GDR head Erich Honecker at the 30th anniversary of the GDR in East Berlin in 1979 – the world would witness a big, sloppy lip-plant. Paris Match splashed Régis Bossu’s iconic black-and-white image of the socialist snog across a double-page spread. Le Baiser, they called it.

Nikita Khrushchev, Joseph Stalin’s successor, locked lips with USSR chairman Klim Voroshilov when returning from a US visit in 1959. In July 1937, Stalin planted a decidedly non-frigid one on Ivan Spirin, a polar explorer and state hero.

But Brezhnev was the true practitioner. The joke in Russia went that he described a Warsaw Pact comrade “as a politician, rubbish...but a good kisser!”

Aside from the steamy Kremlin, social kissing on the mouth declined with the Black Death.

The courtly handkuss (kiss on the hand) generally went the same way with the fall of the German and Russian monarchies in 1917-18, though hung on longer in Austria. 

But French president Jacques Chirac made it his trademark, playing to the gallery with French élégance. An Associated Press story from 1967 chronicles the sad plight of European diplomats who had chanced it in Washington. One congressional wife jumped back, claiming she had been bitten; another said a stone was missing from her ring. “Chivalry has its drawbacks,” the story observed.

But back to the babies. We see kissing-as-canvassing in William Hogarth’s 1755 series The Humours of an Election

And in a close-fought 1784 Westminster by-election, we read of 24 women out canvassing with kisses – including the Duchesses of Rutland, Argyll, Ancaster, and (somewhat infamously) Devonshire. 

Kissing voters’ wives – now probably frowned upon by CCHQ – was customary fare for the 18th-century candidate. It’s only in the following century that we see the desexualisation of the electioneering kiss, moving to babies as innocuous. 

In 1836, Charles Dickens has his character Pickwick go to witness a post-Reform Act by-election in Eatanswill. “He has patted the babies on the head,” says the candidate’s election agent, trembling with anxiety. Roar of applause. “He has kissed one of ‘em!” Second roar. “He's kissing ‘em all!” The crowd’s shouts are deafening. And the candidate Slumkey coasts home to Parliament.

US presidents Richard Nixon, Grover Cleveland and Benjamin Harrison forswore baby kissing, grasping for a higher-minded political plane. Bernie Sanders, too. 

But how are the rest of today's politicians doing, kiss-wise?

Barack Obama: After two terms, a kisser to be reckoned with. With adults. Apparently he doesn’t relish kissing babies, and has been called fatally ill-at-ease holding one. Full points for his lucky save with a reticent Aung San Suu Kyi in 2014, ending with a perfectly creditable side-hug and ear-kiss.

Pity Michelle, photographed rolling her eyes as Barack went in for the selfie with, say, Danish Prime Minister Helle Thorning-Schmidt in 2013. (For her part, Michelle fobbed off Silvio Berlusconi with a fully outstretched arm, taking no chances.)

David Cameron: Utterly denied by SamCam after his Tory conference speech in October 2015. Lord Grantham says in Downton he spent most of Eton avoiding the kisses of other boys; clearly, the Prime Minister didn’t get much practice while at school.

Angela Merkel: In her first meeting with Nicolas Sarkozy, out she came with a businesslike German handshake just as he ducked for the Gallic kiss. In a moment of British romantic awkwardness last May, during Cameron’s EU reform tour, we saw the Prime Minister lean in, short of closing the deal, as she pulled back and possibly searched for some new regulations to beat him away with.

Hillary Clinton: Is said to enjoy kissing babies. Is said not to enjoy kissing Bill, as in the 2008 Correspondents’ Dinner when she expertly ducked one from him.  And scored one from Obama instead. But maybe she ought to lay off the baby-kissing: a journal article in Political Psychology suggests voters are 15 per cent less likely to vote for women candidates when their adverts evoke female gender stereotypes.

Donald Trump: In August, his baby-kiss in Alabama went viral – the baby’s mother just a bit too keen, the baby’s confusion mingled with slight fear reflecting the views of many of us. “That baby is us,” wrote blogger Stassa Edwards.

It’s a long road from here to the US election in November. And Cameron can look forward to kissing up to Merkel and a hot summer of Italian, Dutch, and even French kisses too.

So this Valentine’s Day, spare a thought for the babies. And the bureaucrats.