Great Britain, also known as the United Kingdom, is a sovereign state in northern Europe which includes England, Wales, Scotland and Northern Ireland. It is governed under a constitutional monarchy and a democratic parliamentary system made up of two houses; an elected House of Commons and an appointed House of Lords. It has a population of more than 62 million iand has the world's seventh-largest economy by nominal GDP. It is predominantly a Christian country, although successive waves of migration have contributed to the growth of other faiths. It is a member of the European Union as well as the Commonwealth of Nations, the Council of Europe, G7, G8, G20, NATO, the Organisation for Economic Co-operation and Development (OECD) and the World Trade Organization.