Debt

The work of Carmen Reinhart and Ken Rogoff (RR) on public sector debt ratios, and their relationship with GDP growth, has been extraordinarily influential in academic and policy circles since 2010. Before this week, their statistical analysis, based on a 200-year database which they had painstakingly assembled covering dozens of countries, had appeared to establish an important stylised fact: that debt ratios above 90 per cent were associated with much lower rates of GDP growth than debt ratios under 90 per cent. The sudden drop in growth at a debt ratio similar to that reached in many developed economies acted as a wake up call to governments and encouraged the adoption of austerity programmes.

This week, a paper by Thomas Herndon, Michael Ash and Robert Pollin (HAP) argued that the RR stylised fact was based on simple statistical errors, including a spreadsheet error which RR have now acknowledged. Their critique of the original RR stylised fact promises to establish an alternative conventional wisdom, which is that high public debt ratios are never damaging for GDP growth. But the truth is more complicated than that, and far less certain.