Did you know that there are not 20 member countries in the G20?
As world leaders gather for this year's summit in Hangzhou, China, here’s a brief guide to what the G20 is, who’s invited and why there are more than 20 countries in the club.
So, what is it?
The G20, short for "Group of 20", is made up of 19 countries: Argentina, Australia, Brazil, Canada, China, France, Germany, India, Indonesia, Italy, Japan, South Korea, Mexico, Russia, Saudi Arabia, South Africa, Turkey, the United Kingdom and the United States, plus the European Union.
Together, members account for roughly 85% of the world economy; that's around three-quarters of global trade and two-thirds of the world’s population.
What do they discuss?
The G20 started in 1999, following the Asian financial crisis, as a forum for finance ministers and central bank governors from the major developed and emerging economies to discuss global financial issues.
Amid the global financial crisis in 2008, it grew into the leaders’ summit, a place where presidents and prime ministers could get together for two days to try to solve the world’s economic problems.
Successive meetings of G20 leaders were held in Washington DC in 2008, London in early 2009 and Pittsburgh in late 2009, and have since become annual fixtures.
In the run-up to summits, senior officials known as "sherpas" thrash out the issues for discussion, with the aim of getting G20 members to reach agreement at the summit. Like sherpas in the Himalayas, they help guide their leaders through often difficult terrain, and do the diplomatic legwork.
There are also meetings of finance ministers and central bank governors, trade representatives and anti-corruption working groups.
Who is invited?
The G20 presidency rotates between members and is picked from different regions each year. In 2015, the G20 host was Turkey. This year it is China’s turn, with the theme: “Toward an innovative, invigorated, interconnected and inclusive world economy.”
Spain is a "permanent invitee", and the G20 host also invites a handful of guest countries as a way of reaching out to non-members. However, to invite more nations to join the G20 would make decision-making too cumbersome, the thinking goes.
The heads of a number of international organizations also participate, including the International Monetary Fund, the United Nations, the World Bank and the World Trade Organisation.
Why the summit matters
While the G7 is made up of rich countries, the G20 manages to get leaders from both developed and emerging economies around the table, representing a far broader range of views.
It has been credited with reaching important agreements such as the trillion-dollar pledge in 2009 to help struggling economies during the global financial crisis.
Sometimes, however, it has proved hard for such a diverse group of countries to reach consensus.
The hope that the G20 agenda would broaden beyond the global economy to include discussion of political issues, such as security and climate change, has not really materialized.
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