A more scientific green economy efficiency indicator is constructed based on OH (2010), and a multiperiod spatial DID model is used to examine the impact of national credit demonstration policies on urban green economy efficiency in a sample of cities above the prefecture level in the Yangtze River Delta. The study confirms the following: (1) The national credit demonstration policy makes a significant contribution to the green economic efficiency of cities, and it is conducive to strengthening awareness of the rule of law in the market to regulate market order. (2) The demand for credit regulation in coastal areas has increased under the new development pattern, and the national credit demonstration policy has effectively enhanced green economy efficiency through institutional supply. (3) Under the national credit demonstration policy, the subprovincial level and above can mobilise more resources for policy refinement and support, reducing transaction costs and improving the efficiency of the green economy. (4) The impact of the national credit demonstration policy on the efficiency of Zhejiang’s green economy is more obvious; but, under the overall framework of the Yangtze River Delta, the policy has a more prominent role in promoting green economy efficiency in other provinces. Policy insights are as follows: (1) Different cities have different degrees of impact on the efficiency of the green economy from the national credit demonstration policy, and they should implement differentiated measures based on regional heterogeneity; (2) regulating the use of administrative resources and avoiding undue administrative intervention are important prerequisites for promoting regional integration to enhance the efficiency of the green economy; and (3) strengthening interprovincial credit policy synergies can help to alleviate administrative distortions of policy implementation and enhance the efficiency of the regional green economy.

Based on the China City Commercial Credit Environment Index (CEI), a more scientific spatial DID model was used to examine the long-term impact of the opening of ports and trading in the late Qing Dynasty on the urban commercial credit environment, taking cities above the prefecture level in the Yangtze River Delta as a sample. The study confirms that: (1) the opening of ports and commerce in the late Qing Dynasty had a significant contribution to the urban commercial credit environment, which was conducive to the transformation of production methods and interpersonal relationships from traditional to modern, and to the improvement of the urban commercial credit environment. (2) Before the signing of the Treaty of Shimonoseki, the local forces of the late Qing Dynasty were resistant to the economic aggression of the Great Powers, and the positive impact of the opening of ports and trading on the commercial credit environment of port cities was more significant, but the impact was not obvious after the signing of the Treaty of Shimonoseki. (3) From the history of the opening of ports for trade in the late Qing Dynasty, the economic aggression of the Western powers against the non-patronage areas by means of the buying class objectively strengthened the concept of rule of law and credit awareness in the local market and exerted a long-term influence on the commercial credit environment of the cities, but the impact of the opening of ports for trade on the commercial credit environment of the patronage areas was not prominent. (4) Cities located in the sphere of influence of the common law powers had a more pronounced impact on the commercial credit environment as their institutions and concepts were more easily transplanted, while the impact of the opening of ports and trading on the commercial credit environment of cities in the sphere of influence of the civil law powers was not significant. Policy Insights: (1) Enhance the ability to negotiate with foreign countries on economic and trade matters from a level-headed world perspective, and be bold and adept at fighting unreasonable rules, standards and requirements in order to better optimise the business credit environment; (2) Regulate the use of administrative resources and avoid undue administrative intervention, which is an important prerequisite for improving the basic system of the market economy to enhance the business credit environment; (3) Emphasise both connotative development to follow a Chinese style modernisation path, and (3) emphasising selective cooperation to promote outward development, promoting the interaction, convergence and matching of domestic and foreign regulations, and continuously improving the regional commercial credit environment.