Studying the urban hierarchical pattern and spatial structure of China using a synthesized gravity model

Abstract

The Gravity Model (GM), one of the most classic models adopted by the domain of social sciences from physics, has been widely used to study the interactions between social identities. Previous research that has used the Gravity Model to study the interactions among cities have mostly used a single variable, such as population or GDP, to represent a city, which does not provide a comprehensive depiction of a city’s influence. This paper develops a Synthesized Gravity Model (SGM) based on the traditional Gravity Model to study the evolution of the hierarchy of the Chinese urban system since the mid-1990s. Under this model, socioeconomic variables are synthesized and are represented by the Influential Factor, while the Function Distance is derived from a Network Analysis that is based on multiple transportation methods. As an improvement on the GM, the SGM is used to accurately establish and represent the nodal structure of China’s urban system, the evolution of its hierarchical structure, and the relationships that exist between the nodal structure and socioeconomic factors. The results based on the SGM indicate that China’s national urban system is characterized by the emergence of urban clusters with stronger inter-city interactions since the 1990s. However, the development among cities within certain urban clusters is not even, although the general pattern indicates a lessening inequality amongst cities. Spatially, while most cities at the top of the hierarchy are located in Eastern China, cities in the center and the west of the country are also gaining higher positions in the hierarchy over time. This paper is dedicated to improving the traditional GM in the applications of urban studies, while the system of Chinese cities is used to validate the SGM.