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 com... https://unitedssports.shop/product-category/football-clothing-mens/