## 4 Results
### Influencing Factors of Coupling Coordination Degree  
The supply and demand of civil aviation passenger transport is a process of multi-dimensional interaction between endogenous forces and exogenous forces, market forces and government forces. In this study, the coupling coordination degree is taken as the explained variable. Referring to the high-frequency indicators in the relevant research results, this study selects the level of economic development, population agglomeration, urbanization level, government support, tourism development level, openness, industrial structure, traffic location conditions, etc. as explanatory variables. The influencing factors of the supply-demand coupling coordination degree of China's civil aviation passenger transport are discussed. (1) Economic development. The higher the level of economic development, the greater the demand for air transport modes as well as provision of capital support for optimizing the allocation of public resources for civil aviation passenger transport supply, which is the material guarantee for the coordinated development of coupling. Specific indicators are expressed as per capita GDP. (2) Population agglomeration. Population agglomeration has an impact on the demand for infrastructure and also drives the vitality of regional demand through agglomeration to enhance the level of demand. The specific indicators are expressed by population density. (3) Urbanization level. The process of urbanization is accompanied by the improvement of urban infrastructure which is attractive to capital and scientific and technological talents and stimulates the improvement of urban production efficiency and the growth of consumer demand. The specific indicators  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Year** & **1** & **Z** & **\(p\)** \\ \hline
2004 & 0.055 & 0.857 & 0.196  
are expressed by urbanization rate. (4) Government regulation. Government investment and infrastructure support have improved the supply capacity of civil aviation passenger transport and optimized the market environment to stimulate the potential demand for passenger transport. Specific indicators are expressed as per capita fiscal expenditure. (5) Level of tourism development. The rise in tourist numbers directly promotes the growth of civil aviation passenger demand. The specific indicators are expressed by the ratio of the number of domestic tourists to the resident population. (6) Opening to the outside world. The improvement of openness can promote the upgrading of regional industrial structure and create a substantial number of jobs to promote population agglomeration. The specific indicators are expressed by the ratio of total import and export volume to regional GDP. (7) Industrial structure. The industrial structure represents the existing condition of industrial resources and the surrounding industrial environment. Adjusting the industrial structure can improve the stability of the urban economy and create conditions for guiding population agglomeration and household consumption. The specific indicators are represented by the proportion of the added value of the tertiary industry in GDP. (8) Traffic location conditions. Railway and aviation are both important components of the regional transportation system, and the construction of railway facilities will affect the air traffic volume. The specific indicators are represented by railway density. Based on the above influencing factors, a two-way fixed-effect model is established. The results of the regression analysis are presented in (Table 4). The regression coefficient for per capita GDP is positive and has passed the significance test at the 1% level, indicating that the level of economic development has a significant impact on fostering the coordinated development of coupling. The regression coefficient of urbanization rate is positive and has passed the significance test at the 5% level, denoting that an increase in the level of urbanization contributes positively to the enhancement of coupling coordination.