The aim of the second chapter is to examine the factors which determine the crop choices of small-holder farmers in Nigeria and how these choices affect productivity and welfare outcomes. Using the two-rounds of LSMS panel data from Nigeria in 2010/11 and 2012/13; the paper starts by re-examining the old arguments surrounding whether small-holder farmers are indeed âefficient-but-poorâ. We find that smallholders are generally efficient in their allocation of resources (after estimating household crop productivity by stochastic frontier analysis) but are not necessarily rational in their crop choices because even when some crops are found to be more productive than others, the less productive crop is often chosen. To figure out why, a treatments effect model is employed to determine farmer selection into the choice of a type of crop in the first stage; and subsequently the impact of their choices on productivity and poverty. We find that access to free inputs, non-farm income and the use of seeds from the previous growing season are important determinants of crop choice. The third chapter aims to examine the effect of the choices smallholder farmers make in terms of what crops they grow on the food security outcomes of the households. This issue is studied using the household level panel data available from the World Bankâs Living Standards Measurement Study (LSMS) and different specifications of propensity score matching models. The empirical estimates suggest that smallholders who grow cash crops have significantly more diverse food options available to them as well as a greater amount of overall food consumption but a greater severity of food shortage when food is scarce. However, there is no effect of crop choice on the total number of days in a week without food. Furthermore, when there are significant effects, these effects are reduced when the access to export markets and fluctuations in international food prices are considered as instruments. The conclusion is that if the policy objective is to improve food security, a careful examination has been carried out on the pre-existing conditions of the households before a crop choice recommendation can be made. In addition, cash crop production should only be encouraged when an adequate support can be provided to link the farmers to the international market and if there can be some government-backed price stabilization measures. The fourth chapter examines the determinants of food availability at the national level from the perspective of food imports in African countries. The system-GMM method is adopted for this purpose to account for the endogeneity of variables in a dynamic model. The results show that past import levels, food aid, armed conflicts, food price fluctuations, as well as overall income per capita levels were some of the influential factors for food-security sufficient food imports.