An empirical study on the economic linkage characteristics of Yangtze River port cities based on discrete second-order derivatives

Rapid economic development cannot be achieved without a well-developed trade in goods of various forms, so it depends on the construction and development of coastal or inland ports. How to coordinate the relationship between ports and cities in the development process is of great significance to the sustainable development of port cities, and is also an important part of the current research on ports. This paper uses gray correlation model to study the correlation between city economic development indexes and port development indexes, and finds that the correlation between GDP and gross industrial output value and port cargo throughput is the largest, and on the basis of gray correlation analysis, the impulse response analysis finds that the growth of total economic volume and gross industrial output value of port cities has an obvious promotion effect on the development of ports in the short term. The research results show that the value added of Nanjing’s tertiary industry drives the port logistics of Nanjing port most significantly; the growth rate stabilizes at 0.006 after the 11th period. The growth of Nanjing port container throughput on the value added of Nanjing’s secondary industry changes most significantly and finally stabilizes at 0.0035.