level data from sources like FAOSTAT and the World Bank’s World Development Indicators. Table 1 provides these statistics for 2010 and 2009, respectively, the years when most of the LSMS-ISA surveys we use were fielded, for the six countries of interest here, in addition to regional and least developed countries (LDC) classification averages. Notice that Ethiopia and Malawi fall above the SSA average reported by FAOSTAT while Niger, Nigeria, Tanzania, and Uganda all fall below. As further ammunition for the claim that fertilizer use in low in SSA, the regional average falls below the average for all LDCs. As a means of comparison to existing micro-evidence from farmers’ fields, the final column shows the average fertilizer use rate described in what we deem to be the largest and most-nationally representative study which includes input rates in recent years.<sup>1</sup>

# **_2.2. Improved crop varieties_**

Because the characteristics of planted seeds will impact the productive capacity of the crop that emerges, the germplasm of seeds is a very important for ensuring and bolstering yields. These characteristics might include more grain, drought (or other climate) tolerance, disease resistance, better complementarity with inorganic fertilizers, etc. While breeding activities exist for a range of other purposes – for example, increasing the nutrient value of crops or more leaf material to help with long term soil health – many of the desired attributes seek to increase productivity or decrease risk, both with the intention of increasing overall yields. The need for and therefore research into how to “improve” varieties is different between crop types. Because maize, a major staple in eastern and southern Africa, is cross-pollinating, progeny hybrid seeds will never directly match those of the parents and vigor decreases with replication. These issues are not important when using open pollinating varieties (OPVs) or when cultivating self-pollinating crops like rice and wheat (Fischer, Byerlee, Edmeades 2009; Smale et al. 2011). The equivalently important crops in western Africa are pearl millet and sorghum, two crops for which breeding did not start until the 1980s since they were not part of Green Revolution advances in the 1960s (Evenson and Gollin 2003).

Internationally cross-comparable studies of improved variety use are not readily found given the importance of different crops across countries, the potential unsuitability of particular improved varieties given differences in agro-ecological conditions, and the difficulty in collecting this information when many seeds can be saved between seasons. Further, neither FAOSTAT nor the World Bank provides disaggregation of seed use by improved or traditional varieties. Instead, the best source of cross-country information on the topic is newly available data from the Consultative Group on International Agricultural Research (CGIAR)’s Diffusion and Impact of Improved Varieties in Africa (DIIVA) project, which estimated the total hectares under 21 improved crop varieties in 29 countries in SSA, including all six of the LSMS-ISA countries, for the 2009/10 season (see Alene et al. 2011 for more on the project and initial findings). In Table 2, we include the statistics for some the main crops in each of the LSMS-ISA countries for which data are available.

Other researchers have used national estimates of seed sales to estimate improved variety adoption rates. For example, for maize, Smale, Byerlee, and Jayne (2011) aggregate data from

> 1 One major reason for different rates of use found throughout studies, we find, is that some researchers refer to the total kilograms of inorganic fertilizer applied while others refer to only the actual nutrient contributions.

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