The Republic of Ireland and the UK joined the European Economic Community, which became the European Union (EU), in 1973. In the 1990s, the Republic of Ireland became part of the European Single Market. People are allowed to travel and sell things between countries in the European Single Market. In the late 20th century the economy grew quickly, and changed from mostly farming to mostly services and industry. The UK, including Northern Ireland, left the European Union in 2020, but the UK and the Republic of Ireland agreed not to control border crossings.