From debt arithmetic to fiscal sustainability and fiscal rules:taking stock and policy lessons

We start by clarifying the role of the interest rate-growth rate differential in debt arithmetic with numerical examples for the Greek economy. In turn, buidling upon this popular approach to fiscal sustainability, which is based on the intertemporal government budget constraint only, we make a number of methodological points that question the quantitative usefulness of standard calculations. Among other things, we argue that a structural approach is needed and this reveals the necessity of fiscal rules according to which fiscal instruments systematically react to public debt imbalances. This naturally enables us to evaluate the EU's fiscal rules and to suggest simple and implementable alternatives. Throughout, we confront our arguments with data from the Euro Area.