Last week, three economists at the University of Massachusetts, Amherst, released a paper criticizing our findings. They correctly identified a spreadsheet coding error that led us to miscalculate the growth rates of highly indebted countries since World War II. But they also accused us of “serious errors” stemming from “selective exclusion” of relevant data and “unconventional weighting” of statistics — charges that we vehemently dispute. (In an online-only appendix accompanying this essay, we explain the methodological and technical issues that are in dispute.)
Our research, and even our credentials and integrity, have been furiously attacked innewspapers and on television. Each of us has received hate-filled, even threatening, e-mail messages, some of them blaming us for layoffs of public employees, cutbacks in government services and tax increases. As career academic economists (our only senior public service has been in the research department at the International Monetary Fund) we find these attacks a sad commentary on the politicization of social science research. But our feelings are not what’s important here.
The authors of the paper released last week — Thomas Herndon, Michael Ash and Robert Pollin — say our “findings have served as an intellectual bulwark in support of austerity politics” and urge policy makers to “reassess the austerity agenda itself in both Europe and the United States.”
A sober reassessment of austerity is the responsible course for policy makers, but not for the reasons these authors suggest. Their conclusions are less dramatic than they would have you believe. Our 2010 paper found that, over the long term, growth is about 1 percentage point lower when debt is 90 percent or more of gross domestic product. The University of Massachusetts researchers do not overturn this fundamental finding, which several researchers have elaborated upon.
The academic literature on debt and growth has for some time been focused on identifying causality. Does high debt merely reflect weaker tax revenues and slower growth? Or does high debt undermine growth?