Paolo Zacchia da keynesblog.com:
Siti e blog di economia non parlano d’altro. Un famoso paper di Carmen Reinhart e Kenneth Rogoff, tra i più citati negli ultimi anni, nel quale si evidenziava l’esistenza di una correlazione tra un alto rapporto debito/PIL (maggiore del 90%) e la bassa crescita, è inficiato da gravi problemi metodologici e addirittura da un banale errore nel foglio di calcolo, tanto che su twitter si parla di #excelgate. Eppure, anche sulla base di questo studio, è stata giustificata l’austerità, il pareggio di bilancio e il “rimettere a posto i conti”, al di qua e al di là dell’Atlantico.
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Paul Krugman sul NYT:
The intellectual edifice of austerity economics rests largely on two academic papers that were seized on by policy makers, without ever having been properly vetted, because they said what the Very Serious People wanted to hear. One was Alesina/Ardagna on the macroeconomic effects of austerity, which immediately became exhibit A for those who wanted to believe in expansionary austerity. Unfortunately, even aside from the paper’s failure to distinguish between episodes in which monetary policy was available and those in which it wasn’t, it turned out that their approach to measuring austerity was all wrong; when the IMF used a measure that tracked actual policy, it turned out that contractionary policy was contractionary.
The other paper, which has had immense influence — largely because in the VSP world it is taken to have established a definitive result — was Reinhart/Rogoff on the negative effects of debt on growth. Very quickly, everyone “knew” that terrible things happen when debt passes 90 percent of GDP.
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Dal blog "Free exchange" di The Economist:
GOVERNMENT indebtedness matters. Default and financial panic are the stuff of finance-minister nightmares. Government borrowing can crowd out private investment, dragging growth down. Yet economists have struggled to specify when a country needs to worry about its debt load. In a 2010 paper Carmen Reinhart, now a professor at Harvard Kennedy School, and Kenneth Rogoff, an economist at Harvard University, seemed to provide an answer. They argued that GDP growth slows to a snail’s pace once government-debt levels exceed 90% of GDP.
The 90% figure quickly became ammunition in political arguments over austerity. Paul Ryan, a Republican congressman, cited their “conclusive empirical evidence” in a budget plan calling for swingeing cuts to public spending. In a February letter to European Union finance ministers Olli Rehn, the vice-president of the European Commission, touted the “widely acknowledged” 90% limit as a reason to press on with European fiscal cuts. Such rhetoric has helped to make the Reinhart-Rogoff number the subject of bitter dispute. And this week a new piece of research poured fuel on the fire by calling the 90% finding into question.
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Zack Beauchamp su ThinkProgress:
Tuesday afternoon, Mike Konczal transformed the debate over austerity and growth by reporting new study finding that a paper by Carmen Reinhart and Kenneth Rogoff that served as one of the principal intellectual justification for austerity turns out to be have been fatally flawed. Its conclusions, for example, were based in part on an elementary Excel coding error (Reinhart and Rogoff, for their part, aren’t conceding the game).
This error is obviously of immense economic and political importance; Matt Yglesias rightly calls it “literally the most influential article cited in public and policy debates about the importance of debt stabilization.” But the young controversy also says something interesting about the way that modern journalists do business, especially as arguments over academic papers becomes a bigger and bigger part of public debate, particularly over economics.
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Matthiew O'Brien su The Atlantic:
For an economist, the five most terrifying words in the English language are: I can't replicate your results. But for economists Carmen Reinhart and Ken Rogoff of Harvard, there are seven even more terrifying ones: I think you made an Excel error.
Listen, mistakes happen. Especially with Excel. But hopefully they don't happen in papers that provide the intellectual edifice for an economic experiment -- austerity -- that has kept millions out of work. Well, too late. As Mike Konczal of the Roosevelt Institute reported, Thomas Herndon, Michael Ash, and Robert Pollin of the University of Massachusetts, Amherst, have found serious problems with Reinhart and Rogoff's austerity-justifying work. That work, which shows that countries with public debt of 90 percent of GDP or more tend to grow slower, omitted data for five of its 19 countries, and used the wrong data for another. The former was, embarrassingly enough, due to an Excel misadventure, and the latter an unrelated issue. If you use all of the (right) numbers, it turns out growth does slow when debt is high, but not nearly as much as Reinhart and Rogoff -- hereafter, R-R -- claimed.
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Andrew Watt su Social Europe:
I won’t repeat the numerous points that have been made in the debate of the past couple of days over the Reinhart and Rogoff paper “Growth in a time of debt”. A useful overview is provided by Bruegel here. I will emphasise a few points based, not on the original paper nor on what recent critics have written, but largely with reference to a journalistic article written by the authors themselves.
The statistical errors and shortcomings (excel mistakes, exclusion of countries, weighting issues etc.), that have dominated the debate are not the key issue.
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