Returns to quality in rural agricultural markets: Evidence from wheat markets in Ethiopia
中文摘要
在许多撒哈拉以南国家，农民无法满足城市对更高质量产品日益增长的需求。尽管文献侧重于提升小农产出质量的生产端约束，但关于市场端约束的证据却很稀缺。使用埃塞俄比亚60个小麦市场的样本，我评估农民是否因供应更高质量的产出而获得价格溢价。我利用了数据的一项独特特征，即精确衡量了可观测以及较难或不可观测的质量属性，并将其与交易价格相关联。可观测属性不能作为较不可观测属性的代理变量。交易价格进一步反映了这一点，表明市场仅奖励可无成本观测的质量属性。然而，这些结果掩盖了跨市场异质性。参与关系契约的农民获得了更高的价格，但对质量的回报相似。在农民对应更多交易商的市场中，可观测质量属性获得了更好的回报；而在其他价值链参与者（即粮食加工商和农民合作社）存在的情况下，不可观测属性获得了回报。回归与机器学习方法均支持这些发现。
Abstract
In many Sub-Saharan countries, farmers cannot meet the growing urban demand for higher quality products. While the literature has focused on production-side constraints to enhance smallholder farmers’ output quality, there is scarce evidence of market-side constraints. Using a sample of 60 wheat markets in Ethiopia, I assess whether farmers received a price premium for supplying higher quality outputs. I exploit a unique feature of the data which precisely measures observable and less or unobservable quality attributes, and relate them to transaction prices. Observable attributes cannot serve as proxies for less observable ones. Transaction prices further reflect this, indicating that markets only reward quality attributes that are observable at no cost. However, these results hide cross-market heterogeneity. Farmers engage in relational contracts receive a higher price but similar rewards for quality. Observable quality attributes are better rewarded in markets with more traders per farmer, while unobservable attributes are rewarded in the presence of other value chain actors (i.e., grain millers and farmer cooperatives). Both regression and machine learning approaches support these findings.