The European Union (EU) is an economic and political union of 27 member states, located primarily in Europe. Committed to regional integration, the EU was established by the Treaty of Maastricht on 1 November 1993 upon the foundations of the pre-existing European Economic Community. With almost 500 million citizens, the EU combined generates an estimated 30% share (US$18.4 trillion in 2008) of the nominal gross world product.
The EU has developed a single market through a standardised system of laws which apply in all member states, ensuring the freedom of movement of people, goods, services and capital. It maintains common policies on trade, agriculture, fisheries and regional development. A common currency, the euro, has been adopted by sixteen member states that are thus known as the Eurozone. The EU has developed a limited role in foreign policy, having representation at the WTO, G8 summits, and at the UN. It enacts legislation in justice and home affairs, including the abolition of passport controls between many member states which form part of the Schengen Area. Twenty-one EU countries are also members of NATO.
An international organisation sui generis, the EU operates through a hybrid system of supranationalism and intergovernmentalism. In certain areas, it depends upon agreement between the member states; in others, supranational bodies are able to make decisions without unanimity. Important institutions and bodies of the EU include the European Commission, the Council of the European Union, the European Council, the European Court of Justice, and the European Central Bank. The European Parliament is elected every five years by member states' citizens, to whom the citizenship of the European Union is guaranteed.
The EU traces its origins to the European Coal and Steel Community formed among six countries in 1951 and the Treaty of Rome in 1957. Since then the union has grown in size through the accession of new countries, and new policy areas have been added to the remit of the EU's institutions.