Group membership and certification effects on incomes of coffee farmers in Uganda
研究发现，乌干达罗布斯塔咖啡农的认证对净农场收入无显著影响，但成员身份时长解释了20个百分点的收入差异；而新成立的阿拉比卡咖啡农群体认证带来151%的收入增长，部分归因于更高程度的垂直整合。
Discrepancies in certification effects on smallholder incomes have been found in scientific literature. Unobserved farmer-group heterogeneity is a likely reason. For the long-standing Robusta coffee farmer-groups in Uganda, we find no significant effect of certification on net-farm income. But, we find 20 percentage point differences in net-farm income between certified and non-certified farmers explained by membership duration. In contrast, the recently founded certified Arabica coffee farmer-groups have positive net-farm income effects of 151 per cent, partly explained by a higher degree of vertical integration. With or without certification, long-standing group membership is found to have positive income effects.