# **1. Introduction**

Development theory suggests that improved agricultural productivity is a primary pathway by which societies can begin down the path of economic transformation and growth and out of subsistence level poverty (Johnston and Mellor 1961; Schultz 1964). Three (potentially complementary) paths exist for increasing agricultural output: increase input use, adopt productivity-enhancing technologies, and/or increase the efficiency in use of existing inputs and technologies. Widespread evidence suggests that most smallholder farmers are “poor but efficient” (Schultz 1964; Sherlund, Barrett, Adesina 2002), such that the third of these offers only limited leverage for anything more than modest, one-off productivity gains. Most growthinducing and poverty-reducing sustained agricultural growth then comes from expanded input use, especially of modern inputs – like improved seed, fertilizers and other agro-chemicals, machinery, and irrigation – that embody improved technologies. Asia and Latin America enjoyed tremendous increases in agricultural productivity in a relatively short period of time through rapid and widespread uptake of yield-enhancing modern agricultural inputs (Johnson, Hazell, Gulati 2003). Moreover, the bulk of the economic gains from the development and diffusion of modern inputs accrued to poor consumers as supply expansion outpaced demand growth, driving down real food prices and improving diets (Evenson and Gollin 2003).

Sub-Saharan Africa (SSA) did not participate to the same degree in the Green Revolution of the 1970s-1980s. Dissatisfied with the perceived slow progress of agricultural and food market liberalization policies, several SSA countries have made public commitments to increasing input use via the Abuja Declaration and, more broadly, under the Comprehensive Africa Agriculture Development Programme (CAADP). As an extension, several governments have recently reinstated or revitalized agricultural input subsidy schemes aimed at promoting access to chemical fertilizers and improved seeds (Minot and Benson 2009) with variable success (Jayne and Rashid 2013). In contrast to the awareness resulting from these subsidy programs, irrigation and mechanization have received far less attention, with a few notable exceptions (Houssou et al. 2013; Takeshima, Nin-Pratt, Diao 2013). That neglect may have translated into stagnation or even the reversal of progress in their promotion (Mrema, Baker, Kahan 2008; Van Koppen 2003). Meanwhile, external factors such as record high international food prices, urbanization, the rapid growth of a middle class, and transformation of some food marketing channels may have changed on-farm incentives and resulted in updates to farm management practices, including modern input use (Reardon et al. 2009). A growing international dialogue on and increased awareness about climate change and soil erosion may also be influencing farmers’ practices (Nelson et al. 2010).

Amid these changes and pressures, a major and fundamental gap remains in our understanding of the current input landscape at the country and continent level. While myriad studies look at some facet of modern input use throughout Sub-Saharan Africa, no studies, to our knowledge, focus specifically on broad patterns of farmer input use behavior or on comparisons within and among countries, and especially not in the 21st century, since the onset of what seems an African agricultural renaissance in concert with the various changes previously described. Apart from a very small set of countries where nationally-representative household survey data exist, most knowledge of modern input use is currently derived from macro-level statistics, which cannot capture the heterogeneity in within-country conditions and are prone to issues of data reliability 1