Debt and growth revisited: In a paper presented last January at the annual meeting of the American Economic Association, Carmen Reinhart of the University of Maryland and Kenneth Rogoff of Harvard, the authors of the celebrated history of financial crises, This Time It’s Different: Eight centuries of financial folly; conceit and money, looked at the link between different levels of debt and countries’ economic growth over the last two centuries. One finding: countries with a gross public debt exceeding about 90% of annual economic output tended to grow a lot more slowly. For rich countries above the 90% threshold, average annual growth was about two percentage points lower than for countries with public debt of less than 30% of GDP.