Clive Crook has it exactly right in describing the Eurozone:
The basic contradiction was foreseen many years ago. In a single-currency system, policymakers lack the most powerful tool for helping individual economies adjust to setbacks: interest rates set according to national conditions. To succeed, a single-currency system needs either large fiscal transfers (so fiscal policy can do what monetary policy can’t) or highly integrated labor markets (so the unemployed can move to stronger markets to find work), and preferably both. The euro area has neither, and its governments, even after an epic sovereign debt crisis, have no plans to do much about it.
