The Big Four, also known as G4, refers to France, Germany, Italy and the United Kingdom. France and the United Kingdom are official nuclear-weapon states and are permanent members of the United Nations Security Council with the power of veto, which enables any one of them to prevent the adoption of any "substantive" draft Council resolution, regardless of its level of international support. The United Kingdom is the only country of the Big Four which is not a member state of the European Union having ended its membership in 2020 after a referendum was held in 2016 which resulted in a narrow majority vote in favour of leaving the bloc. France, Germany, Italy and the United Kingdom are considered major European economic powers and they are the Western European countries individually represented as full members of the G7 and the G20. They have been referred to as the "Big Four of Europe" since the interwar period. The term G4 was used for the first time when French President Nicolas Sarkozy called for a meeting in Paris with Italian Prime Minister Silvio Berlusconi, Prime Minister of the United Kingdom Gordon Brown and Chancellor of Germany Angela Merkel to consider the response to the financial crisis during the Great Recession. The Organisation for Economic Co-operation and Development describes them as the "Four Big European Countries".