Deluded by the convergence of bond yields that followed the euro’s launch, investors fed a decade-long private-sector credit boom in Europe’s less-developed periphery countries, and failed to recognize real-estate bubbles in Spain and Ireland, and Greece’s slide into insolvency. When growth slowed sharply and credit flows collapsed in the wake of the Great Recession, budget revenues plummeted, governments were forced to socialize private-sector liabilities, and fiscal deficits and debt soared.