At present, the economic development in Hubei Province has initially entered new era of “one principal two deputy, multi-polar development”. In order to further explore the future of urban development, we ranked prefecture cities in Hubei Provinces with the intensity model of central place function. Meanwhile, according to 32 selected indicators, we investigated the economic linkage between these cities wit h improved gravity model and principal component analysis model. Our results show that: 1) Regarding intensity value of central city z = 2, 0.9, 0.6 as the boundary, 12 cities can be divided into four levels with Wuhan in level 1; Yichang, Xiangyang and Jingzhou in level 2; Huangshi, Shiyan, Jingmen, Xiaogan, Huanggang, Xianning in level 3; the remaining cities in level 4, respectively. 2) According to the economic linkage value, the economic linkages between cities are classified into three levels: closely related, generally related and weakly related. Among them, the generally related and weakly related linkages are most likely caused by the cities’ own economic development structure or their long geographical distance from the economic central city.
In recent years, along with the continuous development of economic globalization, the mode of regional economic integration and urban agglomeration has increasingly become the mainstream in various regions of the world. Through these modes, cities become more competitive in the global economic competition and specialization. The prominent representatives like the European Union, the North American Free Trade Area, the urban agglomeration of the Atlantic coast in the northeastern United States and the urban agglomeration of the Pacific coast of Japan have not only accelerated the circulation of various resources within their regions, promoted the optimization of industrial structure, but also further strengthened the significance of the regions in the global economic landscape.
Hubei Province is located in the “waist of the Yangtze River” and plays a decisive role in the construction of urban agglomerations in the mid-Yangtze. Moreover, as the only mega-city in the central region, Wuhan, the capital of Hubei Province, its economic linkages with other cities in the province play a decisive role in the economic development of Hubei Province and will have a huge impact on the economic development of urban agglomerations in the mid-Yangtze. It can be concluded that at present, China implements the strategy of the Yangtze River Economic Belt and vigorously promotes the urban agglomeration in the mid-Yangtze, which is the most precious opportunity for the future development of Hubei province. Hubei should seize the opportunity, take Wuhan as the core competence to promote the economic development coordination of all the cities and further strengthen the economic linkages with each other, so as to enhance the competitiveness and importance of Hubei province in the national even the international economic environment.
The essence of urban economic linkage is to promote the economic links between cities through the mutual circulation of resources such as people, things and information between cities. The measurement of economic linkages between cities is to measure the closeness of economic linkages between cities through various quantifiable indicators. The related research of regional economic linkages has been a hot research topic in the western countries which have developed urban agglomeration. Starting from using gravitation models to do quantitative analysis of regional spatial linkages (WJ Reilly, 1929), foreign experts and scholars continuously explore quantitative analysis of regional spatial linkages, making the theory of urban economic linkages measurement theory continuously enriched and improved. After WJ Reilly, some scholars applied the law of universal gravitation to the study of urban agglomeration (GK Zipf, 1942) or used the theory of break point to calculate the interaction between city and region based on gravitational model (PD Converse, 1949). Some applied the input-output measurement model to measure the regional economic spatial linkage (Walter Isard, 1951). The measurement scope is not only limited to the regional spatial economic linkage, but also gradually expands to the aspect of city’s functional linkage and the outward service.
Domestic research on urban economic relations started later, and initial research was limited to qualitative analysis. Until 1990, the mathematical measurement model was applied. For the specific model, the current domestic scholars mainly use the gravity model proposed by WJ Reilly or improve the gravity model and interval input-output model, or use social network analysis, geo-economic linkage matching analysis and other methods to measure. And because the reform and opening-up policy of China is a process from the coast to the inland as well as from the point to the surface, the urban agglomerations in the eastern coastal areas are more mature and their economic linkages are closer. Therefore, studies of most of the scholars are related to area of eastern coast. Le Zhang, Yongjun Ma (2013), Xiangjun Ou and Liping Xue et al. (2015) respectively analyzed the spatial linkage of urban space in Zhejiang and Jiangsu Provinces by using gravity model and social network model. They analyzed the economic linkage direction, link intensity and the differences between the central cities, pointed out the direction of economic development in the two provinces [
Based on the previous studies, this paper takes 12 prefecture-level cities in Hubei province as the research content. First of all, takes the index system developed by the Urban Division of National Bureau of Statistics and the research group of urban statistics of China statistical society as reference. Secondly, establishes the index system of urban economic linkage measurement based on the evaluation indicators adopted by the above scholars, considering the quantifiability and the availability of index. Then, with the help of the intensity model of central place function, combines grading method by natural crack point to classify the city. After that, uses the principal component analysis model to evaluate the comprehensive economic intensity of 12 cities and sort them according to their scores. Finally, this paper analyzes and estimates the intensity of the economic linkages between the 12 cities in Hubei Province and provides some suggestions for the future construction, planning and development policy of the urban agglomeration, which will further promote the urban development in the mid-Yangtze.
In order to quantify and evaluate the economic comprehensive economic intensity of the city, the corresponding index system must be established in accordance with the principle of completeness and science. Based on the existing index system, this paper chooses a comprehensive index system of urban economic development including human resources, economic resources, social development resources, infrastructure resources and ecological protection resources.
Human resources are the most active and valuable resources for urban development. People are both the main body of social wealth and the main driving force for maintaining social progress. The population as well as the quality and structure of the population will have far-reaching and direct influence for a city. Therefore, five indicators are selected for human resources: Year-end Population, natural population growth rate, the proportion of registered unemployed population in the total population in urban areas, the proportion of tertiary industry employees in the total population, the population density.
Economic resources are important aspects that directly reflect the current strength of cities as well as the closeness of spatial relationships with other cities. The current economic scale and economic structure will have a significant impact on the overall economic development. However, the selection of indicators of economic resources should not only include the stock indicator but also the incremental indicator. It is necessary to reflect not only the activity level of the internal economy but also the external economy linkage. Therefore, we should select 10 indicators of economic resources including: GDP, The ratio of tertiary industry and GDP, The balance of deposits and loans of financial institutions at the end of the year, Total industrial output value, Total volume of tourist transport, Total freight volume, Business income of postal, Total retail sales of social consumer goods, The actual amount of foreign investment, The social development resources. The economic development of a city can not only pursue short-term development but also the long-term development, so that the city can achieve sustainable economic development. However the indicators that support the sustainable development of urban economy are often the implicit indicators that indirectly promote the current economic development such as science and education. Therefore, we should select 8 social development resources: fiscal revenue, science and technology expenditure, education expenditure, number of Internet broadband users, number of college students per 10,000 people, the public library collection per hundred people, number of hospitals and clinics, the number of people participating in urban basic medical insurance.
Infrastructure construction not only provides more superior hardware conditions and external environment for the development of urban economy, but also is an important aspect of a city in attracting foreign talents. Furthermore, it relates to the direct interests of the residents living condition in the city. Therefore, eight indicators are selected for the infrastructure resources: the length of drainage pipes, the total water supply, the total social electricity consumption, the number of cars owned by each 10,000 people, the urban road area per capita.
The ecological protection resource is the basis for maintaining a city, it provides the most basic place and material resources. Good ecological system is the most fundamental guarantee for the sustainable development of a city. In the process of urban construction and development, we should not only pay attention to the indicators that reduce the damage to the ecological environment, but also focus on the indicators that are conducive to improve the ecological system. Therefore, four indicators are selected for ecological protection resources: green coverage rate of built-up area, utilization of general industrial solid waste, centralized treatment rate of sewage treatment plant, harmless treatment of household garbage [
As the 32 indicators belong to 5 different aspects, the dimensions of the indicators are not uniform, and their promotion effects on urban development are also different, so the indicators need to be treated in a non-dimensional method. For the conventional positive and negative indicators, this paper standardize them by using the extreme value, it can be seen in the formula 1:
{ x i = ( x i − min x i ) / ( max x i − min x i ) positiveindex x i = max x i − x i / max x i − min x i negativeindex (1)
where x i is the value of index i. However, for the neutral indexes like natural population growth rate and the population density, obviously, it is not it is impossible to standardize them directly by using the above formula. So they need to be transformed respectively. Examining the authoritative information we know that: at present, in order to maintain the sustainable development of the population in our country, under the precondition of opening the two-child per family policy, the natural growth rate of our country’s population should be maintained at about 5.5%. Meanwhile, for the population density, the common international standard 500 people / km 2 is relatively reasonable. Therefore, the method of dealing with the neutral index in this paper is as follows: Taking the common policy as the optimal standard, calculate the absolute value of the difference between each index of the 12 cities and the optimal standard. The smaller the absolute value of the difference is, the better the value is. Therefore,