Iran is an energy superpower and the Petroleum industry in Iran plays an important part in it. In 2004 Iran produced 5.1 percent of the world’s total crude oil (3.9 million barrels (620,000 m3) per day), which generated revenues of US$25 billion to US$30 billion and was the country’s primary source of foreign currency. At 2006 levels of production, oil proceeds represented about 18.7 percent of gross domestic product (GDP). However, the importance of the hydrocarbon sector to Iran’s economy has been far greater. The oil and gas industry has been the engine of economic growth, directly affecting public development projects, the government’s annual budget, and most foreign exchange sources. In FY 2009, for example, the sector accounted for 60 percent of total government revenues and 80 percent of the total annual value of both exports and foreign currency earnings. Oil and gas revenues are affected by the value of crude oil on the international market. It has been estimated that at the Organization of the Petroleum Exporting Countries (OPEC) quota level (December 2004), a one-dollar change in the price of crude oil on the international market would alter Iran’s oil revenues by US$1 billion. In 2010, Iran, which exports around 2.6 million barrels of crude oil a day, was the second-largest exporter among the Organization of Petroleum Exporting Countries. In the same year, officials in Iran estimate that Iran's annual oil and gas revenues could reach $250 billion by 2015. According to IHS CERA estimate, oil revenue of Iran will increase by a third to USD 100 billion in 2011 even though the country is under an extended period of U.S. sanctions. Iran plans to invest a total of $500 billion in the oil sector before 2025.