Public debt sustainability is a concern in many countries. In the US, as the economic linchpin of the developed world, public debt has exceeded 130% of GDP and is causing heated debate, in Congress as well. In the EU, the financial crisis, the pandemic, and the energy transition (with effects augmented by the war in Ukraine) have caused public debts to soar; there are countries in the euro area (Greece, Cyprus, Italy, France, Belgium, Spain, Portugal) with public debts that range between 100% and 175% of GDP. By the way, the ECB was forced to intervene through special operations to save the Eurozone during the sovereign debt crisis.