Update December 19, 2014: Although the main point of my column is to emphasize the importance of putting negative paper currency interest rates in the monetary policy toolkit now rather than a decade or two from now (with particular urgency for the European Central Bank and the Bank of Japan), I know that for many readers, the reprise of the Spring 2013 media furor about Carmen Reinhart and Ken Rogoff’s work is equally salient. Personally, I believe eliminating the zero lower bound is much more important as whether debt lowers economic growth even when it doesn’t cause a debt crisis, but the issue of debt and growth does need to be addressed as well.
I had a chance to read Ken Rogoff’s and October 2013 FAQ http://scholar.harvard.edu/rogoff/publications/faq-herndon-ash-and-pollins-critique. Substantively, I think this is a good response to the Thomas Herndon, Michael Ash and Robert Pollin paper (linked there) that started the media furor in Spring 2013. But my own substantive concerns are not those. They are the concerns that Yichuan Wang and I detail in our two Quartz columns and two other posts on Reinhart and Rogoff’s work:
In my view, these posts by Yichuan Wang and me are a good example of how, in Clay Christensen’s terms, the disruptive innovation of the economics blogosphere is beginning to move upscale and challenge traditional economics outlets such as working papers and journal articles.
I hope that, taken as a whole, what I write on my blog puts things in the context of the literature, and—through links—gives the kinds of references that are rightly considered important for academic work. In any case, for me the major source of the not inconsiderable number of references I have had in my academically published work come from other people telling me about work related to my own. The same thing happens online. I deeply appreciate the many links people send me in tweets and in more private communications.
Although it is natural for an individual blog post to be be much less complete than a working paper or journal article, I hope to achieve a reasonable balance between breadth and depth in this blog as a whole. And of course, the relative difficulty of putting mathematical equations in Tumblr means I will choose the working paper format once the number of equations needed to make a point exceeds a certain threshold.
To repeat, although Thomas Herndon, Michael Ash and Robert Pollin’s paper definitely piqued my interest and Yichuan’s interest and so led to our analysis of Carmen Reinhart and Ken Rogoff’s postwar data, I am critical of the substance of Carmen and Ken’s work based on my work with Yichuan, not based on the work of Thomas Herndon, Michael Ash and Robert Pollin.
In relation to our own critique of Carmen and Ken’s work, let me make three substantive points:
- Nonlinearity. In our last piece on Reinhart and Rogoff’s work, http://blog.supplysideliberal.com/post/55484991854/quartz-25-examining-the-entrails-is-there-any
- Yichuan and I look nonlinearly at how different levels of debt are related to growth beyond what one would expect from looking at past growth alone. It would be nice to have more evidence total, but on its face, the hint has a higher growth rate after controlling for past growth at a 90% debt to GDP ratio than at a 50% debt to GDP ratio. And we do suggest that what little evidence there is in the data suggests that, say, 130% debt to GDP ratio is associated with lower growth beyond what would be predicted by past growth than a 90% debt to GDP ratio, though a 130% debt to GDP ratio and a 50% debt to GDP ratio give about the same level of growth beyond what would be predicted by past growth alone. On theoretical grounds, it seems plausible to me, though far from an open-and-shut case that high enough debt levels would cause problems for economics growth. That thinking has led me to argue persistently that monetary stimulus is better than fiscal stimulus because it does not raise national debt. See for example my post “Monetary vs. Fiscal Policy: Expansionary Monetary Policy Does Not Raise the Budget Deficit.”But exactly how high that is matters a lot when people can’t be convinced of the virtues of negative interest rates so that fiscal stimulus remains an issue. I consider the nonlinear smoother result that (given what power there is in the postwar data set) the line is the same at a 130% debt to GDP ratio as at a 50% debt to GDP ratio, even after correcting for “illusory growth” on the part of Ireland and Greece as painting a considerably different picture than someone would get from reading Carmen Reinhart and Ken Rogoff’s, or Carmen Reinhart, Vincent Reinhart and Ken Rogoff’s work.
- Is controlling for past GDP growth appropriate? In my view, yes. I consider the past income growth controls important because countries that are generally messed up are likely to have both high debt and low growth. That doesn’t mean the high debt causes low growth. Most of the discussion has focused on reverse causality, but I consider the positive correlation across many dimensions of bad policy to be another big issue. I worry that the past income controls would make it hard to detect whether or not debt overhangs are followed by long-lasting low-growth periods, as Carmen, Vincent and Ken argue. But without some other way to control for the many, many other possible bad policies besides debt (which goes beyond the kind of growth accounting regressions that Ken’s FAQ document points to as strong evidence in favor of the view that debt might slow growth) this seems to me to point toward genuine empirical agnosticism about whether debt lowers growth as the right conclusion. (Theoretical arguments are a different matter.)
- Does the prewar data strongly bolster the case the debt slows growth? Here, it depends on what the question means. The prewar data were not as readily available as the postwar data, so Yichuan and I did not analyze them. And so I don’t know what they say, once subjected to the kind of empirical exercises I would like to subject them to. I would love to see an analysis like the one the Yichuan and I did on the postwar data applied to the prewar data. That said, the prewar data may answer the question of whether a given debt level lowered growth under the gold standard, or with prewar institutions that were weaker than current institutions. So I have my doubts about how much guidance it can give to policy now. Monetary policy in particular, had advanced dramatically since the pre-World War II era, even before the ongoing revolution against the paper currency standard.
Did Carmen and Ken overstate their case?
While I feel confident that Yichuan’s and my substantive critique has not been adequately addressed, I am much less confident about claims I made in “Righting Rogoff on Japan’s monetary policy” about how policy-makers interpreted Carmen and Ken’s work (and how they could have been expected to have interpreted it, given what was written).
Ken’s FAQ document points to the 2010 Voxeu article “Debt and Growth Revisited” as something that could have provided more balance to policy makers in interpreting Carmen (and Vincent) and Ken’s work. Because policymakers might be more likely to read a Voxeu article than an academic paper, this Voxeu piece is an important touchstone for whether Carmen and Ken overstated the strength of the empirical evidence in favor of the idea that high public debt slows down growth in the range that was relevant to policy in the last few years.
The issue I have with the Voxeu article “Debt and Growth Revisited” is that it never mentions the fact that the normal standard of establishing causality in economics is to find a good instrument, or some other source of exogeneity or quasi-exogeneity. In other words, the inherent difficulty of establishing causality in this kind of data is never mentioned. Here is how strongly Carmen and Ken suggest in their Voxeu article “Debt and Growth Revisited” that there is causal evidence despite the highly endogenous nature of the data:
Debt-to-growth: A unilateral causal pattern from growth to debt, however, does not accord with the evidence. Public debt surges are associated with a higher incidence of debt crises.9 This temporal pattern is analysed in Reinhart and Rogoff (2010b) and in the accompanying country-by-country analyses cited therein. In the current context, even a cursory reading of the recent turmoil in Greece and other European countries can be importantly traced to the adverse impacts of high levels of government debt (or potentially guaranteed debt) on county risk and economic outcomes. At a very basic level, a high public debt burden implies higher future taxes (inflation is also a tax) or lower future government spending, if the government is expected to repay its debts.
There is scant evidence to suggest that high debt has little impact on growth. Kumar and Woo (2010) highlight in their cross-country findings that debt levels have negative consequences for subsequent growth, even after controlling for other standard determinants in growth equations. For emerging markets, an older literature on the debt overhang of the 1980s frequently addresses this theme. …
… We have presented evidence – in a multi-country sample spanning about two centuries – suggesting that high levels of debt dampen growth.
I appreciate the note of uncertainty in the sentence
Perhaps soaring US debt levels will not prove to be a drag on growth in the decades to come.
But I feel that for the typical policy maker reading the Voxeu article, this note of uncertainty is largely cancelled out by the next sentence:
However, if history is any guide, that is a risky proposition and over-reliance on US exceptionalism may only prove to be one more example of the “This Time is Different” syndrome.
The phrase “if history is any guide” phrase in particular suggests that the historical evidence gives some clear guidance, and the sentence as a whole points to an interpretation of “Perhaps soaring US debt levels will not prove a drag on growth in the decades to come” as simply making a bow toward random variation around a regression line rather than expressing any uncertainty about what the causal regression line for the effect of debt on growth says before other random factors are added in.
In any case, saying “Perhaps soaring US debt levels will not prove to be a drag on growth in the decades to come” is not the same as if Carmen and Ken had said
Of course further research could overturn the suggestion we find in the evidence that high debt lowers growth, and there are always many difficulties with interpreting historical evidence of this kind.
Of course, there is always the possibility that Carmen and Ken said almost exactly that, in a forum that most policy makers would have noticed, but one that Idid not notice. (My own reading is ridiculously far from comprehensive.) If so, I would love to get a link to it. Ideally, I would like to see the main text of Ken’s FAQ document collect in its main text all the details (including of course venue or outlet and date) about all the strongest caveats and cautions against overreading that Carmen, Vincent and Ken wrote about their work.
One extremely important note that the FAQ document does have is this quotation from Reinhart, Reinhart, and Rogoff (2012), “Public Debt Overhangs: Advanced-Economy Episodes since 1800.” (Journal of Economic Perspectives, 26(3)):
This paper should not be interpreted as a manifesto for rapid public debt deleveraging exclusively via fiscal austerity in an environment of high unemployment. Our review of historical experience also highlights that, apart from outcomes of full or selective default on public debt, there are other strategies to address public debt overhang, including debt restructuring and a plethora of debt conversions (voluntary and otherwise). The pathway to containing and reducing public debt will require a change that is sustained over the middle and the long term. However, the evidence, as we read it, casts doubt on the view that soaring government debt does not matter when markets (and official players, notably central banks) seem willing to absorb it at low interest rates – as is the case for now.”
This suggests to me that Paul Krugman went overboard in his criticism of Carmen and Ken—at least before he backed off somewhat. I am not up on all the details, but it is my understanding that some of Paul Krugman’s stronger criticisms against Carmen and Ken in terms of providing intellectual backing for austerity might have been better leveled against other influential economists, such as Alberto Alesina. But I would need a lot of help to know whether such criticisms were even appropriate for other influential economists such as Alberto. For the record, the current Wikipedia article on Alberto Alesina says:
In October 2009 Alesina and Silvia Ardagna published Large Changes in Fiscal Policy: Taxes Versus Spending, a much-cited academic paper aimed at showing that fiscal austerity measures did not hurt economies, and actually helped their recovery. In 2010 the paper Growth in a Time of Debt by Carmen Reinhart and Kenneth Rogoff) was published and widely accepted, setting the stage for the wave of fiscal austerity that swept Europe during the Great Recession. In April 2013 some analysts at the IMF and the Roosevelt Institute found the Reinhart-Rogoff paper flawed. On June 6, 2013 U.S. economist and 2008 Nobel laureatePaul Krugman published How the Case for Austerity Has Crumbled in The New York Review of Books, noting how influential these articles have been with policymakers, describing the paper by the ‘Bocconi Boys’ Alesina and Ardagna (from the name of their Italian alma mater) as “a full frontal assault on the Keynesian proposition that cutting spending in a weak economy produces further weakness”, arguing the reverse.
Thus, Wikipedia conflates Carmen and Ken’s views with those of Alberto Alesina and Silvia Ardagna.
But just as Carmen and Ken’s views should not be conflated with Alberto and Silvia’s views, neither should my views be conflated with Paul Krugman’s. Soon after Thomas Herndon, Michael Ash and Robert Pollin’s paper came out, I wrote in Quartz:
Unlike what many politicians would do in similar circumstances, Reinhart and Rogoff have been forthright in admitting their errors. (See Chris Cook’s Financial Times post, “Reinhart and Rogoff Recrunch the Numbers.”) They also used their response to put forward their best argument that correcting the errors does not change their bottom line. Given the number of bloggers arguing the opposite case—that Reinhart and Rogoff’s bottom line has been destroyed—it is actually helpful for them to make their case in what has become an adversarial situation, despite their self-justifying motivation for doing so. And though I see a self-justifying motivation, I find it credible that Reinhart and Rogoff’s original error did not arise from political motivations, since as they note in their response, of their two major claims—(1) debt hurts growth and (2) economic slumps typically last a long time after a financial crisis—the claim that debt hurts growth is congenial to Republicans, while the claim that it is normal for slumps to last a long time after a financial crisis is congenial to Democrats.
The results from the fairly straightforward data analysis that Yichuan and I did made me somewhat less sympathetic to Carmen and Ken. Nevertheless, I think they spoke and wrote in good faith. Errors of omission are a different issue, and there we all stand condemned, in a hundred different directions for each of us.
It is from the perspective that we all stand condemned for errors of omission of one type or another, that I hope my words in “Righting Rogoff on Japan’s monetary policy” are taken. I also urge you to distinguish carefully between simply reportingone side of the Spring 2013 debate about Reinhart and Rogoff’s work, and things I say on my own behalf: principally that Ken does not challenge policy-maker conventional wisdom as much as I would like to see.
Carmen and Ken literally did not have time enough to defend themselves adequately back in Spring 2013. Now that the dust has cleared, I would be glad to see them do more to tell their side of the story.
This update is my effort to make up for some of my own errors of omission when I wrote “Righting Rogoff on Japan’s monetary policy.” In particular, I thought wrestling with Ken’s FAQ document was the least I could do to give a little more voice to Carmen and Ken’s side of the story. (To the extent that you were persuaded by Thomas Herndon, Michael Ash and Robert Pollin’s paper, or were persuaded by unjustified accusations of bad faith on Carmen and Ken’s part, you should take a close look at that FAQ document.)