Now that the proposition of a 90 percent threshold (of public debt-to-GDP above which countries' economic growth would significantly slow) associated with the work of Carmen Reinhart and Ken Rogoff has been refuted, it's important that the debate now turn to the critical issue of how best to achieve growth moving forward.
On this point, one important aspect to keep in mind is that the uses toward which public debt is directed and the composition of public debt tend to have a significant impact on a country's economic growth.
A recent study by the IMF entitled "Public Debt and Growth" appears to support this view. The study, which examined the public debt dynamics in over 30 countries, found that, although the elasticity of growth with respect to public debt is -0.02, the elasticity of other variables that positively impacts growth offsets this number. For instance, as Iyanatul Islam has noted, the study shows that the elasticity of growth to initial years of schooling is above 2.0.
In other words, it's quite likely that public debt directed toward productive uses has the effect of supporting growth by cancelling out some of the negative effects associated with high public debt that impede growth.
These are the sort of issues policymakers should be discussing moving forward. I think it would go a long way to help us get out of the economic doldrums we're facing today.
Manmohan and Jaejoon, Public Debt and Growth, IMF, July 2010