How and to what extent do development programs deliver intended outcomes in a rapidly evolving sector? 3ie’s recent evaluation of the IDEA project (Increasing Income, Diversifying Diets, and Empowering Women in Aquaculture), implemented by WorldFish in northwest Bangladesh, offers valuable insights in this regard and helps ensure that impact is not just visible, but well understood and correctly attributed. The study (see report) contributes to 3ie’s broader mission of generating high-quality evidence on what works—and under what conditions.
Bangladesh’s aquaculture sector has witnessed what is often described as a “quiet revolution1.” Fish farming has expanded over fifteenfold since the 1980s, transforming the livelihoods of millions across the country (FAO). In the northwest divisions of Rangpur and Rajshahi, the growth has been strong as pond-based fish production rose sharply by 26% in Rangpur and 28% between 2018 and 2023, according to Bangladesh Directorate of Fisheries’ statistics. Despite this rapid expansion, gaps persist in nutrition outcomes and women’s economic participation. The IDEA project sought to further boost smallholder aquaculture productivity by empowering women, and improving nutrition outcomes through innovative trainings, financial and market linkages. Rangpur and Rajshahi were selected for their high concentration of small and medium aquaculture households and their importance as fish-producing regions with functioning but uneven markets. They offered a relevant setting to test whether aquaculture growth could be more inclusive and nutrition sensitive.
To rigorously assess the project’s impact, 3ie conducted a large-scale randomized controlled trial (RCT), comparing communities that received IDEA support with those that did not.
The evaluation revealed important insights into how sector-wide growth interacts with targeted interventions—and why understanding these dynamics is critical for designing future aquaculture and livelihoods programs. Aquaculture outcomes - such as pond productivity, fish sales, and household income - improved markedly across all study areas between 2020 and 2023. The entire sector was advancing rapidly, with commercialization, improved input adoption, and market activity lifting outcomes for both project and non-project farmers alike. To understand how and why this happened, it is useful to walk through the theory of change (ToC).
- Productivity gains without project influence: The ToC assumed productivity was held back by knowledge and input gaps that extension could address. The findings suggest that core aquaculture knowledge and input access were already strong at baseline, with similar improvements seen in both project and non-project areas. Productivity and commercial input use did rise—but these patterns align more with wider sectoral momentum than with project-specific effects.
- Extension services that could not shape markets: The ToC envisioned Local Service Providers (LSPs) as scalable, gender-sensitive market shapers. In reality, COVID compressed implementation into a short window, and LSP rollout had limited time to mature. Providers mainly responded to existing market signals, focusing on commercially viable species, which positioned them more as technical advisors than agents of broader market change.
- Commercialization without inclusive gains: The income pathway expected farmer groups and gender-responsive strategies to help smallholders, especially women, capture more value. Most groups, however, formed late and had little time to function as effective market actors, with few women-only groups. As markets rewarded larger, high-value species of fish, commercialization progressed - but without clear gains for smallholders or women.
- Nutrition pathways undermined by market incentives: The nutrition pathway anticipated that social and behavior change communication (SBCC) and increased fish availability would boost consumption of fish, particularly small and indigenous (SIS) varieties. In practice, nutritional activities reached relatively few households and started late, while baseline fish consumption was already high. As markets expanded, economic incentives increasingly favored commercially valuable species, and production of nutritionally important SIS declined.
IDEA’s results reflect the challenges of working in a system that was already evolving rapidly. The ToC was built around constraints that were becoming less relevant in a fast-commercializing context, highlighting the complexities of aligning project design with changing ground realities.
This underscores the value of independent, evidence-based impact evaluations for learning and future program design. Without a credible counterfactual, one might have concluded—based on rising income and productivity alone—that the project was a great success. Instead, the study revealed that these improvements reflected broader sectoral trends rather than project-specific impacts. Such insights are not setbacks, they are lessons. They help implementers refine future program designs, identify where public investments add value, and understand how local markets and knowledge systems evolve.
Bangladesh’s aquaculture transformation is real and impressive. The IDEA evaluation adds to this narrative by showing how quickly the sector is moving and how future initiatives can adapt to sustain momentum. Development partners like WorldFish can build on these findings to target innovation, inclusion, and sustainability, while evaluators like 3ie continue to ensure that decisions are grounded in rigorous evidence. Impact evaluations remind us that progress without attribution is not enough. Knowing why change happens and ensuring that interventions genuinely add value is what turns good intentions into meaningful, measurable development outcomes.
1Ricardo Hernandez, Ben Belton, Thomas Reardon, Chaoran Hu, Xiaobo Zhang, Akhter Ahmed. 2017. The “Quiet Revolution” in the Aquaculture Value Chain in Bangladesh, Aquaculture, June 15, 2017. https://www.sciencedirect.com/science/article/pii/S0044848616312236?via%3Dihub
