Research on the Impact of Green Bond Discount Policy on the Marginal Cost of Financing of Private Enterprises

目的：探讨绿色债券贴息政策对民营企业融资边际成本的实际影响，评估其在缓解融资难题中的政策成效。方法：构建双重差分模型，基于2018~2023年绿色债券发行数据，选取获得贴息支持的民营企业作为处理组，量化政策实施前后融资成本变动。结果：贴息政策显著降低民营企业融资边际成本，平均下降约37个基点，效果在小微企业与环保导向行业中更为显著。信用溢价压缩与市场交易活跃度提升为主要作用机制。结论：绿色贴息政策具备显著的成本缓解效应与信用增信价值，应强化制度联动，提升政策激励的结构性与持续性。Objective: To explore the actual impact of the green bond discount policy on the marginal cost of financing of private enterprises, and to evaluate its effectiveness in alleviating the financing problem. Methods: A double difference model was constructed. Based on the data on green bond issuance from 2018 to 2023, private enterprises supported by discount interest were selected as the treatment group to quantify the changes in financing costs before and after the implementation of the policy. Results: The discount policy significantly reduced the marginal cost of financing for private enterprises by an average of about 37 basis points, and the effect was more significant in small and micro enterprises and environmental protection oriented industries. The compression of credit premium and the improvement of market transaction activity are the main mechanisms. Conclusion: The green discount policy has a significant cost mitigation effect and credit enhancement value. We should strengthen the system linkage and improve the structure and sustainability of policy incentives.