Euro
History
The euro was established by the provisions in the 1992 Maastricht Treaty. To participate in the currency, member states are meant to meet strict criteria, such as a budget deficit of less than 3% of their GDP, a debt ratio of less than 60% of GDP (both of which were ultimately widely flouted after introduction), low inflation, and interest rates close to the EU average. In the Maastricht Treaty, the United Kingdom and Denmark were granted exemptions per their request from moving to the stage of monetary union which resulted in the introduction of the euro. (For macroeconomic theory, see below.)
Euro-18