The single monetary policy - even during the run-up to EMU - has provided many countries with an unprecedented degree of price stability. Trade has intensified and financial markets in Europe are integrating fast. Businesses, consumers and investors alike are seeing the benefits. And even more is to be gained. Three countries are currently “member states with a derogation” (Article 122 of the Treaty).
This basically means that they do not yet participate in European Monetary Union, implying that there is still some scope for enlargement within the EU as it is at present. The single currency is the consequent development of the common market. The status of “member state with a derogation” is designed to be an intermediate stage on the path to full EMU membership.