The Organization of the Petroleum Exporting Countries (OPEC, /ˈoʊpɛk/ OH-pek) is an intergovernmental organisation of 14 nations, founded in 1960 in Baghdad by the first five members (Iran, Iraq, Kuwait, Saudi Arabia, and Venezuela), and headquartered since 1965 in Vienna, Austria. As of September 2018, the then 15 member countries accounted for an estimated 44 percent of global oil production and 81.5 percent of the world's "proven" oil reserves, giving OPEC a major influence on global oil prices that were previously determined by the so called "Seven Sisters” grouping of multinational oil companies.