I had the privilege of attending the Karl Brunner lecture by Mario Draghi1 at ETH Zurich on 1 October. In his lecture, the former ECB president described an arrangement with two parts: an independent central bank responsible for price stability, and governments able to manage their debts without leaning on it. He then added a condition that is harder to legislate into existence: an economy that grows. The arithmetic of debt and growth The shorthand we all learned in Econ 101 is r minus g: the average interest rate paid on outstanding government debt minus nominal GDP growth, including inflation....