Chad's primarily agricultural economy will continue to be boosted by major foreign direct investment projects in the oil sector that began in 2000. At least 80% of Chad's population relies on subsistence farming and livestock raising for its livelihood. Chad's economy has long been handicapped by its landlocked position, high energy costs, and a history of instability. Chad relies on foreign assistance and foreign capital for most public and private sector investment projects. A consortium led by two US companies has been investing $3.7 billion to develop oil reserves - estimated at 1 billion more..barrels - in southern Chad. Chinese companies are also expanding exploration efforts and are currently building a 300-km pipeline and the country's first refinery. The nation's total oil reserves are estimated at 1.5 billion barrels. Oil production came on stream in late 2003. Chad began to export oil in 2004. Cotton, cattle, and gum arabic provide the bulk of Chad's non-oil export earnings.