Measuring the effectiveness of agricultural R&D in Sub-Saharan Africa from the perspectives of varietal output and adoption: initial results from the diffusion of improved varieties in Africa project - Alene, Arega; Yigezu, Yigezu; Ndjeunga, Jupiter; Labarta, Ricardo; Andrade, Robert; Diagne, Aliou; Muthoni, Rachel; Simtowe, Franklin; Walker, Thomas (International Food Policy Research Institute, 2011)