support to taxation, depending on governments‟ objectives and on the level of the world price for different commodities (Kasara, 2007; Anderson and Masters, 2009). The nature of pre-reform agricultural policies has been identified as a key determinant of supply response in Asia (Rozelle and Swinnen, 2004).<sup>4</sup> There are thus reasons to expect the impact of reforms in SSA to be crop- and country-specific and to have varied depending on the time of their introduction.

Third, the imperfect nature of inputs and credit markets in Africa and the difficulty to enforce contracts, imply that the impact of reforms could vary depending on the size of input requirements for different crops. Indeed, when production requires the use of costly inputs and interlocking of input and output markets is necessary, introducing competition not only affects the prices received by farmers, but also the sustainability of input-credit schemes (Dorward _et al._ , 2004; Delpeuch _et al._ , 2010).

Finally, many external factors interact with the reform of specific agricultural markets, among which, variations in world market conditions, domestic macro-economic policies, conflicts and, most importantly, weather conditions (Meerman, 1997).<sup>5</sup> With a few exceptions (e.g. Brambilla and Porto, forthcoming and Kaminski _et al._ , 2011), these external factors are rarely formally accounted for in studies of agricultural transition in SSA. In particular, while the impact of weather on agricultural productivity is estimated in the specialised literature on the link between climate and agricultural productivity (e.g. Fontaine and Janicot, 1996 and Le Barbé _et al._ , 2002 on the inter-annual and interdecadal variability of the West African monsoon), we have not seen it included as a control in the structural adjustment literature.

This paper aims to illuminate long-standing debates about the impact of structural adjustment in SSA agriculture by addressing all of the above-mentioned issues. We adopt a novel quantitative, sectoral and long-term approach, in which we control for country-specific determinants and incorporate detailed information on the pace of reforms, the nature of post-reform market structure, pre-reform policies and weather conditions. Such detailed information is taken from two new datasets. First, we use the market structure indices compiled in Delpeuch and Leblois (2011) to inform the

> 4 Swinnen and Rozelle (2004) show how supply responses were intimately linked to the nature of agricultural policies under state control in different regions of Asia and Europe: where the state had tried to force industrialization in part by taxing agriculture, eliminating distortions resulted in output growth; where the state had tried to stimulate agricultural production by subsidizing inputs or output, market pricing resulted in output decline.

> 5 Differences in the legal and economic environment and enabling institutions have also been identified as a determinant of supply response (Jayne et al., 1997; Kherallah et al., 2002). However, this factor is more likely to explain broad differences in outcome between developing regions than within SSA, where the legal and economic environment and enabling institutions are relatively homogeneously low.

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