European Union representation within those institutions, a practice often referred to as "pooling of sovereignty". To become a member, a country must meet the Copenhagen criteria, defined at the 1993 meeting of the European Council in Copenhagen. These require a stable democracy that respects human rights and the rule of law; a functioning market economy; and the acceptance of the obligations of membership, including EU law. Evaluation of a country's fulfilment of the criteria is the responsibility of the European Council. No member state has yet left the Union, although Greenland (an autonomous province of Denmark) withdrew in 1985. Article 50 of
Greenland a tight fiscal policy since the late 1980s, which has helped create surpluses in the public budget and low inflation. Since 1990, Greenland has registered a foreign-trade deficit following the closure of the last remaining lead and zinc mine that year. More recently, new sources of ruby in Greenland have been discovered, promising to bring new industry and a new export from the country. (See Gemstone industry in Greenland). Air transportation exists both within Greenland and between the island and other nations. There is also scheduled boat traffic, but the long distances lead to long travel times and low frequency.