(CNN) Here's a look at the Organization of the Petroleum Exporting Countries, headquartered in Vienna, Austria.
The purpose of OPEC is to "coordinate and unify the petroleum policies of its Member Countries and ensure the stabilization of oil markets in order to secure an efficient, economic and regular supply of petroleum to consumers, a steady income to producers and a fair return on capital for those investing in the petroleum industry."
OPEC members collectively supply about 28.89% of the world's crude oil production.
Together, OPEC members control about 79.49% of the world's total proven crude reserves.
OPEC member countries monitor the market and decide collectively to raise or lower oil production in order to maintain stable prices and supply.
A unanimous vote is required on raising or lowering oil production.
Each member country controls the oil production of its country, but OPEC aims to coordinate the production policies of member countries.
Oil and energy ministers from OPEC member countries usually meet twice a year to determine OPEC's output level. They also meet in extraordinary sessions whenever required.
Read More: Oil and Gasoline Fast Facts
Algeria - 1969-present
Congo - 2018-present
Equatorial Guinea - 2017-present
Gabon - 1975-1995; 2016-present
Iran - 1960-present
Iraq - 1960-present
Kuwait - 1960-present
Libya - 1962-present
Nigeria - 1971-present
Saudi Arabia - 1960-present
United Arab Emirates - 1967-present
Venezuela - 1960-present
Angola - 2007-2024
Ecuador - 1973-1992; 2007-2020
Indonesia - 1962-2009; 2016
Qatar - 1961-2019
September 14, 1960 - OPEC is formed in Baghdad, Iran, Iraq, Kuwait, Saudi Arabia and Venezuela.
November 6, 1962 - OPEC is registered with the United Nations Secretariat (UN Resolution No. 6363).
1973-1974 - Due to United States support of Israel in the Arab-Israeli conflict, the members of OPEC decide to raise the cost of oil from $3/barrel to around $12/barrel.
October 1973 - OPEC issues an embargo against the United States, halting oil exports. Customers in the United States experience long lines at gas stations and shortages.
March 18, 1974 - At an OPEC meeting, seven members lift the ban on exports to the United States: Algeria, Saudi Arabia, Kuwait, Qatar, Bahrain, Egypt and Abu Dhabi. Libya and Syria refuse to drop the ban, and Iraq boycotts the talks.
December 31, 1974 - Libya lifts its oil embargo against the United States.
November 2007 - Ecuador rejoins OPEC after a 15-year absence.
May 2008 - Indonesia announces that it will leave OPEC in 2009.
January 1, 2009 - Indonesia suspends its membership in OPEC.
January 1, 2016-November 30, 2016 - Indonesia rejoins OPEC, but suspends its membership after 11 months.
July 2016 - Gabon rejoins OPEC.
May 25, 2017 - Equatorial Guinea joins OPEC.
June 22, 2018 - OPEC announces that the Republic of the Congo has joined the organization.
December 3, 2018 - Qatar's state oil company, Qatar Petroleum, announces that the country will leave OPEC on January 1, 2019. One of OPEC's oldest members, Qatar says it plans to focus on natural gas production.
January 1, 2020 - Ecuador leaves OPEC.
March 2020 - To offset the collapse in demand caused by the coronavirus pandemic, OPEC unveils a plan to reduce output among its members by 1 million barrels per day, and says it will seek an additional 500,000 barrels per day in cuts from longstanding allies, including Russia.
April 1, 2021 - OPEC and allied producers announce that they have agreed to gradually increase their output over the next three months. The move follows a sharp increase in oil prices, and a call from the United States to keep energy affordable.
October 5, 2022 - OPEC and its allies, known as OPEC+, announce they will cut oil production by 2 million barrels per day, the biggest cut since the start of the pandemic.
January 1, 2024 - Angola leaves OPEC. Oil minister Diamantino Azevedo said earlier that membership was not serving Angola's interests.