The G-20 is made up of the finance ministers and central bank governors of 19 countries: Argentina, Australia, Brazil, Canada, China, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Turkey, the United Kingdom and the United States of America, and also the European Union who is represented by the rotating Council presidency and the European Central Bank. To ensure global economic fora and institutions work together, the Managing Director of the International Monetary Fund (IMF) and the President of the World Bank, plus the chairs of the International Monetary and Financial Committee and Development Committee of the IMF and World Bank, also participate in G-20 meetings on an ex-officio basis. The G-20 thus brings together important industrial and emerging-market countries from all regions of the world. Together, member countries represent around 90 per cent of global gross national product, 80 per cent of world trade (including EU intra-trade) as well as two-thirds of the world's population. The G-20's economic weight and broad membership gives it a high degree of legitimacy and influence over the management of the global economy and financial system.

(Source: http://www.g20.org)