The socialist-oriented economy depends primarily upon revenues from the oil sector which contributes practically all export earnings and about one-third of GDP. The oil revenues and a small population give Libya one of the highest per capita GDPs in Africa. Farming is severely limited by the small amount of fertile soil and the lack of rainfall, and Libya must import about 75% of its food. Libya has invested much of its oil profits in the development of other parts of its economy, including agriculture, industry, and mining. The government is working to develop medium and heavy industry to help reduce Libya's dependence on imports.