Chad's primarily agricultural economy will continue to be boosted by major oilfield and pipeline projects that began in 2000. Over 80% of Chad's population relies on subsistence farming and stock raising for its livelihood. Cotton, cattle, and gum arabic provide the bulk of Chad's export earnings, but Chad will begin to export oil in 2004. 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 barrels in southern Chad. Oil production came on stream in late 2003.