This paper examines sources of agricultural growth in sub-Saharan Africa. Growth in the stock of traditional inputs (land, labor, livestock) remains the dominant source of output growth. Growth in modern input use was of secondary importance, but still accounted for a 0.2-0.4% annual growth rate in three of four sub-regions.Econometric results support earlier studies that suggest that land abundance may be a constraint on land productivity growth. Growth in agricultural exports and historic calorie availability had positive impacts on productivity. These latter results suggest that positive feedback effects exist between export performance and food security on one hand and agricultural productivity on the other. • Corresponding author. 1 The views expressed are the authors' and are not necessarily those of USDA. 0169·5150/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0169·5150(95)01143·9

This paper examines sources of agricultural growth in sub-Saharan Africa. Growth in the stock of traditional inputs (land, labor, livestock) remains the dominant source of output growth. Growth in modern input use was of secondary importance, but still accounted for a 0.2-0.4% annual growth rate in three of four sub-regions.Econometric results support earlier studies that suggest that land abundance may be a constraint on land productivity growth. Growth in agricultural exports and historic calorie availability had positive impacts on productivity. These latter results suggest that positive feedback effects exist between export performance and food security on one hand and agricultural productivity on the other. 0169·5150/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0169·5150(95)01143·9

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Ranch and livestock sector impacts are estimated for a 10% reduction in grazing on federal lands in the West to protect threatened and endangered species. Two sets of species are considered. One set targets species listed due to grazing and the other targets species whose recovery plans include restrictions on grazing. Using the former set and assuming no substitution between alternative sources of forage, the grazing restriction reduces annual ranch and livestock sector incomes by $54.4 and $83.7 million, respectively. For the latter set, the decreases in ranch and livestock sector incomes are $47.7 and $73.4 million, respectively.