Oil was discovered in Libya in 1958 and is about 95% of the country's export income. Oil is about 25% of Libya's GDP. Other exports include natural gas, salt, limestone and gypsum. Because so much of the country is desert, Libya has to import about 75% of its food. It does grow wheat, barley, olives, dates, citrus, peanuts, soybeans and many vegetables. In 1984, a pipeline was started to bring underground water from the Sahara to coastal areas for irrigation. The pipeline which will take 25 years to complete has been estimated to cost about $25 billion. It is called the Great Man-made River, and is the largest water development scheme in the world.