Member nations and their daily average oil production in 2010 (in parentheses) are as follows:
Saudi Arabia (10 million barrels per day)
Iran (4.2)
United Arab Emirates (2.8)
Kuwait (2.5)
Venezuela (2.5)
Iraq (2.5)
Nigeria (2.4)
Angola (1.9)
Algeria (1.8)
Libya (1.7)
Qatar (1.6)
Ecuador (0.5)
OPEC was founded in Baghdad, Iraq, in 1960, in response to U.S. President Dwight Eisenhower's decision to limit imports from Venezuela and Middle Eastern countries in favor of Mexican and Canadian oil. The cartel has since sought, with varying degrees of success, to control the flow and price of oil in the world.
Since 1965, OPEC countries' share of world oil production has hovered between 42 and 44 percent. It is currently at 42 percent.
The organization's success depends on its political and economic cohesion, which has always been dubious. The organization's two big rivals, Saudi Arabia and Iran, are chronically at loggerheads, with Saudi Arabia pushing with freer flows of oils and Iran pushing more more restrictive flows, in order to drive the price of oil up. The first major split between Iran and OPEC over production quotas occurred in 2000.
Political divisions have intensified since the beginning of the Arab Spring, with Iran further undercutting Saudi policies, and Qatar supporting military intervention against Libya, though both nations are members of OPEC.
In 1990, Iraq invaded Kuwait, and Ara nations responded by joining the U.S.-led coalition to drive Iraq out of Kuwait. And throughout the 1980s, the Iran-Iraq war kept both those member nations in intense opposition, though both needed steep production of oil to finance their war.