A monetary union is stable as long as its members find it more beneficial to be in that union rather than outside it. This stability is easier to achieve if everybody plays by the same rules. In a monetary union, economic well-being is not simply a domestic question.
Member States’ economies influence each other, which is why a monetary union is more attractive if all its members are prospering. Accordingly, Europe’s decision-makers have given themselves common rules to guide fiscal and economic policies. 2  BIS central bankers’ speeches  These rules have repeatedly been broken.