Agricultural training is a potentially effective method to diffuse relevant new technologies to increase productivity and alleviate rural poverty in Sub-Saharan Africa (SSA). However, since it is prohibitively expensive to provide direct training to all the farmers in SSA, it is critically important to examine the extent to which technologies taught to a small number of farmers disseminate to non-trained farmers. This paper investigates the technology dissemination pathways among smallholder rice producers within a rural irrigation scheme in Tanzania. As an innovative feature, we compare the performance of three categories of farmers: key farmers, who receive intensive pre-season training at a local training center; intermediate farmers, who are trained by the key farmers; and other ordinary farmers. By collecting and analyzing a unique five-year household-level panel data set, we estimate difference-indifferences models to assess how the gap in performance evolve as the technologies spill over from the trained farmers to the ordinary farmers. To disentangle the technology spillover process, we also examine the extent to which social and geographical network with the key and intermediate farmers influences the adoption of technologies by the ordinary farmers, by incorporating social relationship variables into spatial econometric models. We found that the ordinary farmers who were a relative or residential neighbor of a key or intermediate farmer were more likely to adopt new technologies than those who were not. As a result, while the key farmers' technology adoption rates rose immediately after the training, those of the non-trained ordinary farmers caught up belatedly. As the technologies disseminated, the paddy yield of the key farmers increased from 3.1 to 5.3 tons per hectare, while the yield of the ordinary farmers increased from 2.6 to 3.7 tons per hectare. Our results suggest the effectiveness and practical potential of farmer-to-farmer extension programs for smallholders in SSA as a cost effective alternative to the conventional farmer training approach.

Although social capital is considered to be a key instrument for common pool resource (CPR) management, its effect among heterogenous players such as upstream and downstream farmers along an irrigation canal is not clear. Using a combination of lab-in-the-field experiments to measure social capital and household survey data in a unique natural experimental setting, this study shows that upstream farmers with higher trust toward the downstream farmers are more likely to be satisfied with their water usage. This finding is consistent with the hypothesis that upstream farmers with higher trust demand less water and leave more water in a canal because they expect reciprocal behaviour from downstream farmers. Since the incentive structures of irrigation management closely resemble those of the standard experiments to measure social capital, this finding also provides a unique case study of the real-world relevance of these experiments.

This study investigates how pesticide use by neighbouring farmers affects a given farmer's pesticide use. Although it is common knowledge that pesticide use has spatial externalities, few empirical economic studies explicitly analyse this issue. Applying a spatial panel econometric model to plot-level panel data for Bohol, Philippines, this study shows that pesticide use, especially for herbicides, is spatially correlated, although there is no statistically significant spatial correlation in unobserved shocks. This implies that farmers apply pesticides by referring to the behaviour of neighbouring farmers rather than responding directly to the intensity of their own infestation.

Background Frequent mutations of the COVID-19 virus, such as the Delta and Omicron variants, have prolonged the pandemic. Rich countries have approved the booster shots (3rd doses) of vaccine, but this causes further delay of vaccination in developing countries. This raises the risk of further mutations, which may lower the efficacy of currently available vaccines. As herd immunity by universal vaccination is essential to end the pandemic, the COVID-19 Vaccine Global Access (COVAX) facility has been established to provide developing countries with subsidized vaccines. However, a critical issue is that the developing countries also need to effectively deploy vaccines to citizens. Although this argument suggests positive effects of good national governance on vaccination coverage, to the best of our knowledge, there is no cross-country evidence on the role of national governance in increasing the coverage of COVID-19 vaccines among citizens. The goal of this study was to examine the association between the national governance and vaccination coverage among developing countries. Methods Using cross-country data, an ordinary least squares regression was conducted to examine the association between the national governance index and three outcomes: (1) the number of days until the administration of the first dose in the country since December 2019, (2) the number of doses per 100 citizens as of the end of July 2021, and (3) the selection of approved vaccine manufacturers. The results were compared between the model including all countries and the model excluding the member countries of Organisation for Economic Co-operation and Development (OECD). Results A one standard deviation increase in the national governance index was associated with 9.1 days (95%CI: -15.76, -2.43) earlier administration of vaccines in the country, and a 12.1 dose increase (95%CI: 4.76, 19.34) per 100 citizens. These associations were larger in the non-OECD sample. The results also indicated the role of governance in the selection of the administered vaccines. Conclusion The provision of subsidized vaccines alone is not sufficient to control the spread of infection in developing countries; logistical and administrative support should also be offered, especially in countries with poor governance. Trial registration Not applicable

After the seminal work of Durkheim (1897), many subsequent studies have revealed a decline in suicide rates during wartime. However, their main focus was inter-state wars and whether the same argument holds for civil conflicts within a country is an important unresolved issue in the modern world. Moreover, the findings of the previous studies are not conclusive due to unobserved confounding factors. This study investigated the relationship between civil war and suicide rate through a more rigorous statistical approach using the Sri Lankan civil war as a case study. For this purpose, we employed a linear regression model with district and year fixed effects to estimate a difference-in-difference in the suicide rate between the peacetime and wartime periods as well as the contested and non-contested districts. The results indicate that the suicide rate in the contested districts in the wartime was significantly lower than the baseline by 11.8–14.4 points (95% CI 6.46–17.22 and 7.21–21.54, respectively), which corresponds to a 43–52% decline. The robustness of the possible confounding factors was analyzed and not noted to have so much effect as to alter the interpretation of the results. This finding supports the Durkheimian theory, which places importance on social integration as a determinant of suicide, even for civil conflicts.