In an economy with its own fiat currency, the monetary authority and the fiscal authority can ensure that public debt denominated in the national fiat currency is non-defaultable, i.e. maturing government bonds are convertible into currency at par. With this arrangement in place, fiscal policy can focus on business cycle stabilisation when monetary policy hits the lower bound constraint. However, the fiscal authorities of the euro area countries have given up the ability to issue non-defaultable debt. As a consequence, effective macroeconomic stabilisation has been difficult to achieve.
-- Monetary-fiscal interactions and the euro area's vulnerability, European Central Bank Bulletin 2017.
Author's commentary: when the ECB tells you that Euro makes no sense, you should listen.
