The Insurance Properties of Common Debt Issuance

The cost of public debt increases more than proportionally with the debt/GDP ratio. This convexity has one immediate implication in the presence of uncertainty about growth: the average social cost of public debt is higher than the contractual debt service cost embedded in the interest rate. In this EconPol policy report, Daniel Gros explains how Common European debt, which is financed by a pro-rata levy on the output of member states, provides an insurance function because countries which grow less have to contribute less (and vice versa). This insurance function becomes more important the longer the horizon and thus the uncertainty about (relative) economic performance.