The Organization of Petroleum Exporting Countries (OPEC) was formed in September of 1960 with five founding members: Iran, Iraq, Kuwait, Saudi Arabia and Venezuela. Since then its membership has risen to include Qatar (1961), Libya (1962), the United Arab Emirates (1967), Algeria (1969), Nigeria (1971), Ecuador (1973) and Angola (2007).

Indonesia joined in 1962 and suspended its membership in 2009. Gabon was added in 1975 and terminated its membership in 1995. Ecuador suspended its membership in 1995 and resumed it in 2007.

The five founding members of the cartel must all agree on the admission of new members, giving any of the five veto power on expanding the organization. New members must also be approved by three-quarters of the other full members of the group. The cartel’s rules also allow for associate members, countries that do not qualify for full membership but that may be admitted under special conditions. There are currently no associate members of OPEC.

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The data come from OPEC’s 2014 Annual Statistical Bulletin and represents 2013 totals. Members are listed in declining order of oil reserves. We do not include proved reserves of natural gas, which total some 95 trillion cubic meters (about 3.35 quadrillion cubic feet) among the 12 nations, with Iran (34 trillion cubic meters) and Qatar (about 25 trillion cubic meters) claiming well over half the total.

Venezuela
298.40 billion barrels of proved reserves
$373.98 billion in 2013 GDP
Population – 29.99 million

Saudi Arabia
265.79 billion barrels of proved reserves
$745.27 billion in 2013 GDP
Population – 29.99 million

Iran
157.80 billion barrels of proved reserves
$366.26 billion in 2013 GDP
Population – 77.10 million

Iraq
144.21 billion barrels of proved reserves
$229.33 billion in 2013 GDP
Population – 35.10 million

Kuwait
101.5 billion barrels of proved reserves
$184.03 billion in 2013 GDP
Population – 3.96 million

United Arab Emirates (UAE)
97.80 billion barrels of proved reserves
$396.24 billion in 2013 GDP
Population – 8.46 million

Libya
48.36 billion barrels of proved reserves
$73.76 billion in 2013 GDP
Population – 6.30 million

Nigeria
37.07 billion barrels of proved reserves
$515.79 billion in 2013 GDP
Population – 172.29 million

Qatar
25.24 billion barrels of proved reserves
$202.17 billion in 2013 GDP
Population – 2.01 million

Algeria
12.20 billion barrels of proved reserves
$223.86 billion in 2013 GDP
Population – 38.30 million

Angola
9.01 billion barrels of proved reserves
$120.51 billion in 2013 GDP
Population – 19.18 million

Ecuador
8.83 billion barrels of proved reserves
$93.58 billion in 2013 GDP
Population – 15.78 million

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