Bulgaria is a member of the European Union, NATO, and the Council of Europe; it is a founding state of the Organization for Security and Co-operation in Europe (OSCE) and has taken a seat on the United Nations Security Council three times. Its market economy is part of the European Single Market and mostly relies on services, followed by industry—especially machine building and mining—and agriculture. Bulgaria is a developing country with an upper-middle-income economy, very high Human Development Index; although it has the lowest GDP per capita and joint-lowest Human Development Index in the European Union. Widespread corruption is a major socioeconomic issue; Bulgaria ranked as the most corrupt country in the European Union in 2018. The country also faces a demographic crisis, with its population shrinking annually since the late 1980s; it currently numbers roughly seven million, down from a peak of nearly nine million in 1988.