Village-level data from western Sudan cast doubt on the universal applicability of an inverse relationship between farm wealth and production per hectare, and the attendant explanation of imperfect labor markets. Wealthy farmers have higher levels of output per hectare; they use more labor per hectare. Insecurity in renting land, financing constraints and the absence of insurance are the vital elements in explanations of the observed pattern of variation in yields. Examination of the performance of land rental, credit and insurance markets in western Sudan suggest that insurance and financing constraints are the crucial market failures.