Do the Outcomes of Voluntary Sustainability Standards Vary by Midstream Buyer Characteristics? Panel Evidence from Rwanda’s Coffee Sector

Voluntary sustainability standards (VSS) are expected to improve smallholder livelihoods, yet past research finds that their effects vary substantially across contexts. VSS typically operate through group certification, which is often initiated and managed by midstream buyers acting as certificate holders. These buyers are responsible for organizing certification-related activities and ensuring farmer compliance, but they differ in their size, capacities and resources. Such differences may help explain why farmers benefit from VSS to varying degrees. While the literature increasingly recognizes the importance of buyer heterogeneity, quantitative evidence on whether and how it shapes farmer outcomes remains limited. Drawing on a unique three-wave panel dataset (t=2022; 2023; 2024) from Rwanda’s coffee sector covering 845 coffee-producing households, combined with information from 48 midstream buyers to whom these farmers supply coffee, to our knowledge, our study provides the first empirical quantitative evidence on these relationships. The results from the inverse probability weighted generalized linear model show that the relationship between VSS and economic outcomes - yield, prices and profits - varies depending on several midstream buyer characteristics. In particular, certification is associated with higher yield, profit gains and partially prices, when the buyer’s manager has characteristics related to their local credibility and social standing, and when certified buyers operate at a larger scale. Our findings highlight that midstream buyer characteristics are associated with heterogeneity in VSS outcomes for farmers, suggesting that analyses and policy discussions on VSS effectiveness should pay greater attention to these supply chain actors.