  Since the introduction of the euro, many economists have argued that any monetary union faces the risk that the economic developments of some of its members diverge, even if an adequate mix of national policy measures is applied.
They have  BIS central bankers’ speeches  7  called for some form of transfer or fiscal union as a complement to common monetary policy. Some have argued that a monetary union without a minimum of fiscal solidarity cannot persist. At the beginning of Stage Three of Economic and Monetary Union, however, the political will to move in that direction was small.