John Kenneth Galbraith memorably put down his fellow economist Milton Friedman by saying: “Milton’s misfortune was that his policies had been tried.”

The same observation might be made of Carmen Reinhart and Kenneth Rogoff. Especially in Europe, pro-austerity policy makers have tried policies based on their research with catastrophic economic and human consequences. The Harvard economists’ tragedy is not the misuse of a Microsoft Excel spreadsheet but the misuse of Microsoft PowerPoint. They hyped their results. In doing so, they followed the golden rule of tabloid journalism: simplify then exaggerate.

Since the publication in 2011 of their bestselling book, This Time Is Different, and their subsequent research on the relationship between debt and growth, the professors have left no doubt that they believe the data show there is a 90 per cent threshold of debt to gross domestic product beyond which economic growth declines rapidly. Many policy makers have interpreted this rule as a call to reduce debt to below that level for the sake of growth. Profs Reinhart and Rogoff have thus become the intellectual godmother and godfather of austerity.