From certification to agglomeration: Evidence from geographical indications of agricultural products in China
利用中国2008年起逐步推行的农产品地理标志认证作为准自然实验，采用交错双重差分法，发现认证通过强化投入产出联系显著促进了县域农业集聚，但对劳动力市场共享和知识溢出无显著影响。
Abstract Marshallian agglomeration is typically attributed to input–output linkages, labor market pooling, and knowledge spillovers; however, empirical evidence on how these mechanisms operate in agricultural settings remains limited. This paper examines whether and how China's agricultural geographical indications certification fosters agricultural agglomeration. Exploiting the staggered rollout of this certification system since 2008 as a quasi‐natural experiment, we employ a staggered difference‐in‐differences design and find that certification significantly promotes county‐level agricultural agglomeration, primarily through strengthened input–output linkages: it encourages the colocation of upstream producers and downstream processors and deepens local production networks. In contrast, we find no significant effects through labor market pooling or knowledge spillovers. The agglomeration effects are concentrated in plant‐based certifications and are stronger in counties with better market access and transportation infrastructure. Overall, our findings extend Marshallian agglomeration theory to agriculture and provide new causal evidence on how agricultural geographical indications certification contributes to agricultural agglomeration as part of broader sectoral structural transformation.