Experimental design
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We use a randomized control trial (RCT) to examine the relationship between the adoption of modern seed varieties and land use decisions by smallholder farmers. The RCT evaluated the PARRSA program described above in a sample of 92 villages spread across Sud Ubangi, Mongala, and North Ubangi districts of the former Equateur province and across 5 (out of 9) territories in those districts, selected based on their relative accessibility by truck.The sample of villages was stratified based on population size (below or above the median size), remoteness (an indicator of accessibility), and exposure to agricultural extension. Based on this stratification, 32 villages were randomly selected as control villages, and 60 were randomly selected for a pilot subsidy intervention promoting maize, rice, and groundnuts seeds—this paper does not comment on the adoption of cassava, as it was not widely available through the project and is less demanding in terms of soil nutrients.In the 60 treatment villages, households were randomly chosen ahead of the agricultural season to receive discount vouchers for the purchase of modern seed varieties at a subsidized price through a public lottery organized by the PARRSA team. The vouchers could be used for any of four of the main local staple crops and were redeemable (within 3 months) at the stores of local seed multipliers. The level of subsidy offered by the vouchers was randomly varied across recipients to study households’ decisions to purchase modern seed varieties at different effective prices. Seed vouchers offered either a 30%, 60%, 90%, or 100% subsidy for a maximum of 10 kg of cereal or legumes seeds (or equivalent amounts of cassava stems). This provides the exogenous variation needed to analyze the impact of the promotion of modern seed varieties on household land use decisions. In each treatment village, equal shares of vouchers offering each level of subsidy were distributed. Half of the vouchers were randomly assigned to the household heads, and the other half were assigned to the spouse of the household head. In the case of polygamous households, randomization was conducted to determine which spouse would receive the voucher.To assess potential spillovers and general equilibrium effects, the proportion of households receiving a voucher was also varied randomly across villages. In one-third of randomly selected villages, 70% of households received a voucher through this lottery (high density); in one-third of random villages, 45% of households received vouchers (medium density), and in the last one-third of villages, only 20% received vouchers (low density). To maximize power, we pooled together villages with different treatment densities (i.e., with different shares of households that received vouchers). Table Last, as the stores of local seed multipliers tend to be located in distant urban areas, another experimental variation was introduced to assess the influence of high transportation costs. In 35 randomly selected villages, a truck offered the seeds for sale directly in the center of the village a few days after the voucher distribution. This allowed households to redeem their voucher and obtain seeds directly in their own village, saving on travel costs. Vouchers were, in theory, redeemable for cereals, legumes, or cassava. Due to logistical considerations, however, trucks ended up offering both legumes and cereals for sale in the villages, while very limited quantities of legumes were available in the stores. In fact, the Ministry ensured the supply of groundnuts for the trucks, while groundnuts ended up in short supply at the seed multipliers’ offices due to mass buying by other institutional buyers for emergency food aid for the Central African Republic. Although unintended, this variation allows insights to be drawn into the differential impact of the use of cereal versus legume modern seed varieties.In total, 4394 vouchers were distributed across the 60 villages. Random distribution of vouchers in treatment villages was conducted in February 2013. For all varieties, seeds can be re-used in the following seasons (with seeds retaining their improved properties for several seasons). It is important to note that the timing of the distribution of the vouchers in February 2013 was such that it was too late to clear the primary forest that year. In contrast, for the first season of 2014, farmers had time to optimally choose and prepare the plot on which to grow the seeds resulting from the first harvest of these improved seeds. For this reason, we concentrate the analysis on 2014. Survey data confirm farmers re-used the improved seeds and largely did not share them with other farmers.Given the large number of vouchers distributed, and the household level randomization, the study design provides the statistical power to detect the direct impacts of receiving vouchers and differences between different levels of subsidies. The randomized assignment of treatments across villages (with and without truck delivery and control) and across households in treatment villages (different levels of discount vouchers) assures that villages and households exposed to different treatments are similar in expectation. Results are, therefore, by construction unlikely to suffer from bias due to factors such as those that would arise if obtaining a voucher was correlated with the crops that farmers were growing at baseline or with differentiated market access across villages. Even so, with 92 villages and 3 treatment groups, the design is still somewhat vulnerable to potential accidental imbalances. We therefore also show results based on randomization inference, which shows the probability that a similar size treatment effect would have been observed under different hypothetical realizations of the chosen randomization method. The randomization inference results confirm all main findings. For more detailed information on the experimental design, compliance and take-up, and related data collection, see