The Namibian economy has a modern market sector, which produces most of the country's wealth, and a traditional subsistence sector. Namibias chief economic sectors include the extraction and processing of diamonds. Namibia is the fourth-largest exporter of non-fuel minerals in Africa, the world's fifth-largest producer of uranium, and the producer of large quantities of lead, zinc, tin, silver, and tungsten. Half of the population depends on agriculture (largely subsistence agriculture) for its livelihood. Namibia normally imports about 50% of its cereal requirements. The countrys fishing grounds are some of the worlds richest and fish processing is one of the countrys main industrial activities.