International Initiative for Impact Evaluation (3ie)

International Initiative for Impact Evaluation (3ie) promotes evidence-informed equitable, inclusive and sustainable development. 3ie supports the generation and effective use of high-quality evidence to inform decision-making and improve the lives of people living in poverty in low- and middle-income countries. 3ie provides guidance and support to produce, synthesize and quality assure evidence of what works, for whom, how, why, and at what cost.

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Projects

Picture-Based Crop Insurance (PBI)

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Publications

Working Paper

The impact of genetically modified cowpea on yields, postharvest losses, and profitability in Nigeria: Findings from a cluster randomized controlled trial

2025Amare, Mulubrhan; Andam, Kwaw S.; Spielman, David J.; Bamiwuye, Temilolu; Zambrano, Patricia; Chambers, Judith A.; Fasoranti, Adetunji; Popoola, Olufemi

Details

The impact of genetically modified cowpea on yields, postharvest losses, and profitability in Nigeria: Findings from a cluster randomized controlled trial

We assess the impacts of a genetically modified pod borer-resistant (PBR) cowpea variety in Nigeria through a cluster randomized controlled trial conducted in two major cowpea-cultivating states. Our design allows us to examine the impacts of PBR cowpea with and without a package of complementary inputs (fertilizer and insecticides) and in comparison to farmers who received only a conventional improved cowpea variety. Results indicate that farmers who received and planted PBR cowpea experienced significant increases in yield (21 percent) and net margins (49 percent) compared to those growing the conventional variety, with larger gains observed among those provided with the inputs package. Analysis of heterogeneous effects indicates substantial variation in outcomes based on baseline characteristics such as household size, landholding, pest control practices, and wealth. Estimation of group average treatment effects and classification analysis using a causal machine learning approach identify plot size, pesticide use, and assets as key drivers of impact heterogeneity. Findings highlight the need for targeted dissemination strategies to realize the sizable benefits of PBR cowpea for small-scale, resource-constrained farmers.

Year published

2025

Authors

Amare, Mulubrhan; Andam, Kwaw S.; Spielman, David J.; Bamiwuye, Temilolu; Zambrano, Patricia; Chambers, Judith A.; Fasoranti, Adetunji; Popoola, Olufemi

Citation

Amare, Mulubrhan; Andam, Kwaw S.; Spielman, David J.; Bamiwuye, Temilolu; Zambrano, Patricia; et al. 2025. The impact of genetically modified cowpea on yields, postharvest losses, and profitability in Nigeria: Findings from a cluster randomized controlled trial. IFPRI Discussion Paper 2383. Washington, DC: International Food Policy Research Institute. https://hdl.handle.net/10568/178553

Country/Region

Nigeria

Keywords

Africa; Sub-saharan Africa; Western Africa; Impact; Genetically Modified Organisms; Seed Damaging Insects; Pest Resistance; Cowpeas; Randomized Controlled Trials; Machine Learning; Smallholders; Information Dissemination; Yields; Postharvest Losses; Profitability

Language

English

Access/Licence

Open Access

Source

Source record

Project

National Policies and Strategies

Record type

Working Paper

Regional implications of public investments and external shocks in Papua New Guinea: An economywide analysis

2025Dorosh, Paul A.; Fang, Peixun; Pradesha, Angga

Details

Regional implications of public investments and external shocks in Papua New Guinea: An economywide analysis

Improvements in telecommunications have enabled a tremendous increase in the flow of information across Papua New Guinea. Although transport costs remain high between various parts of the main island of Papua New Guinea, as well as between the main island and other parts of the country (e.g. the islands of New Britain and Bougainville to the East), phone and internet conditions enable government, traders and entrepreneurs to share market information that reduces transactions costs and improves market function. Nonetheless, there remain major differences in agricultural production, income sources and demand patterns across regions that are important to take into account in analyzing the impacts of external shocks and formulating development strategies. Earlier work on PNG by Schmidt et al., (2021) explored the effects of Covid-related income and world rice price shocks with a partial equilibrium model of PNG’s rice economy. Diao et al., (2021) used a regional multi-market model to analyze broader effects of Covid-19 and other shocks to agriculture and household incomes in four regions of PNG. Various other studies, including Dorosh and Pradesha (2022) and Diao et al. (2024), used national computable general equilibrium (CGE) models of PNG to analyze exchange rate, terms of trade, and productivity shocks on various household groups. In this paper, we extend these earlier analyses through use of a new regional CGE model that utilizes recent household survey data, including the 2023 IFPRI PNG rural household survey. The plan of this paper is as follows. The next section provides an overview of agriculture and economic growth in PNG over the last decade, highlighting the almost constant share of agriculture in GDP and very low per capita agricultural GDP growth rate. Section 3 describes the regional disaggregation of the PNG economy and the structure of household incomes and expenditure as reflected in the economywide database, the Social Accounting Matrix (SAM), used in this analysis. Section 4 then presents a summary of the regional economywide model. (Details of the model are found in the annexes and in the references included in the paper.) Design of the model simulations and simulation results covering investments in agriculture and transport sectors, as well as world price shocks are discussed in Section 5. Chapter 6 concludes with a summary of the main findings and policy implications, as well as suggested areas for further work.

Year published

2025

Authors

Dorosh, Paul A.; Fang, Peixun; Pradesha, Angga

Citation

Dorosh, Paul A.; Fang, Peixun; and Pradesha, Angga. 2025. Regional implications of public investments and external shocks in Papua New Guinea: An economywide analysis. Papua New Guinea Food Policy Strengthening Working Paper 8. Washington, DC: International Food Policy Research Institute. https://hdl.handle.net/10568/178296

Country/Region

Papua New Guinea

Keywords

Oceania; Public Investment; Shock; Agriculture; Models

Language

English

Access/Licence

Open Access

Source

Source record

Record type

Working Paper

Conflict and agricultural inputs: Impacts on maize yields in Nigeria

2025Amare, Mulubrhan; Andam, Kwaw S.; Balana, Bedru; Olanrewaju, Opeyemi; Omamo, Steven Were

Details

Conflict and agricultural inputs: Impacts on maize yields in Nigeria

While standard agronomic recommendations advocate for increased application of inorganic fertilizer to boost maize yields across sub-Saharan Africa, there is limited understanding of how violent conflict influences smallholder farmers’ fertilizer demand, yield responses, and the overall profitability of fertilizer use. This study addresses this gap by analyzing how exposure to conflict affects input use decisions and the economic returns to fertilizer among maize farmers in Nigeria. Using detailed household-level data and spatially referenced conflict events, we estimate maize yield response functions with respect to nitrogen application and assess the profitability of fertilizer under varying levels of conflict exposure. Our findings reveal three key results. First, the marginal physical product (MPP) of nitrogen is low across the study sample, indicating limited agronomic responsiveness. Second, conflict exposure significantly reduces the likelihood and intensity of fertilizer use, suggesting that insecurity constrains both input access and willingness to invest. Third, conflict lowers the MPP of nitrogen even further, thereby reducing the marginal value-cost ratio (MVCR) and undermining the profitability of fertilizer use. These results highlight the importance of considering conflict as a key external factor that distorts input-output relationships in agricultural production. Insecurity not only affects access to inputs through higher prices and disrupted supply chains, but also alters expected returns, making fertilizer investments less attractive for risk-averse farmers. Recognizing the effects of conflict on fertilizer use and yield response is essential for designing more effective input subsidy programs, targeting strategies, and resilience-building interventions in fragile agricultural systems.

Year published

2025

Authors

Amare, Mulubrhan; Andam, Kwaw S.; Balana, Bedru; Olanrewaju, Opeyemi; Omamo, Steven Were

Citation

Amare, Mulubrhan; Andam, Kwaw S.; Balana, Bedru; Olanrewaju, Opeyemi; and Omamo, Steven Were. 2025. Conflict and agricultural inputs: Impacts on maize yields in Nigeria. IFPRI Discussion Paper 2378. Washington, DC: International Food Policy Research Institute. https://hdl.handle.net/10568/178034

Country/Region

Nigeria

Keywords

Africa; Sub-saharan Africa; Western Africa; Conflicts; Farm Inputs; Maize; Crop Yield; Fertilizer Application; Yield Response Factor

Language

English

Access/Licence

Open Access

Source

Source record

Project

National Policies and Strategies