Uneven inclusion in the global political economy as a site for colonial resource extraction (primarily cotton and crude oil), a global economic system that does not promote nor encourage the development of Chadian industrialization, and the failure to support local agricultural production has meant that the majority of Chadians live in daily uncertainty and hunger. Over 80% of Chad's population relies on subsistence farming and livestock raising for its livelihood. The crops grown and the locations of herds are determined by the local climate. In the southernmost 10% of the territory lies the nation's most fertile cropland, with rich yields of sorghum and millet. In the Sahel only the hardier varieties of millet grow, and with much lower yields than in the south. On the other hand, the Sahel is ideal pastureland for large herds of commercial cattle and for goats, sheep, donkeys and horses. The Sahara's scattered oases support only some dates and legumes. Chad's cities face serious difficulties of municipal infrastructure; only 48% of urban residents have access to potable water and only 2% to basic sanitation.