The development process of regional economic integration, on the one hand, cannot be separated from the development of transportation infrastructure, which makes the flow of commodities and production factors break through the spatial barriers; on the other hand, it cannot be separated from the development and maturity of market economic mechanism, which makes the flow of commodities and production factors break through the market segmentation. In essence, regional economic integration is to eliminate functional and institutional market segmentation, promote the free flow of commodities and factors, and realize the optimal allocation of regional resources and rational division of labor.

The Yangtze river delta economy in the era of high-speed railway

The modern three-dimensional transportation network is under rapid development in the Yangtze river delta region, especially the accelerating construction of high-speed railway network. The length of high-speed railway in operation has reached 5,070.8 kilometers by 2017, accounting for one sixth of the country’s total railway mileage, that makes it one of the regions with the highest train frequency density in China. The arrival of high-speed railway era marks a new stage of economic integration in the Yangtze river delta, which will inevitably bring a great impact on the economic layout of the Yangtze river delta, further accelerate the flow of commodities and production factors, promote the economic integration of Shanghai, Jiangsu, Zhejiang and Anhui provinces, and improve the spatial allocation efficiency of resources.

However, the economic integration of the Yangtze river delta in the era of high-speed railway is bound to readjust the economic spatial pattern of the Yangtze river delta and promote a new round of urban differentiation. For example, from 2010 to 2017, the proportion of GDP in Wenzhou, Taizhou, Ningbo, Shaoxing and Jiaxing and other coastal cities decreased, while that in Hangzhou increased by 2.2%, indicating Zhejiang entering Hangzhou era. Wuxi, Zhenjiang and Suzhou saw their share of the province’s GDP drop by 1.7%, 0.22% and 2.5% respectively, while Nanjing’s rose by 1.02%. The GDP of Nanjing was 56% of that of Suzhou in 2010 and increased rapidly to 68% in 2017, indicating the decline of southern Jiangsu and rise of Nanjing. The GDP proportion of cities along the river, such as Ma ‘anshan and Anqing decreased while that of Hefei increased by 2.4% , making it a star city.

Urban industries devision of labour tend to be vertical

The phenomenon of urban differentiation in the process of economic integration of Yangtze river delta is the reaction of deep adjustment of industrial division of labor among cities. Regional economic integration will promote the gradual weakening of the horizontal division of labor between cities and the gradual strengthening of the vertical division of labor. Horizontal division of labor is manifested as one-city industry system that results in similar industrial structure between cities，further leading to homogeneous competition. At the same time, this kind of system is difficult to adapt to the rapid pace of technological change. The vertical division of labor is the division of labor in the industrial chain. Take a certain industry as an example, from its management and control, research and development, design, procurement, parts production, processing and assembly, to logistics distribution, marketing, after-sales service and many other links, it can be completed in different cities, or distributed among different countries worldwide. It is worth mentioning that the layout of a certain link of an industrial chain depends on the economic development level, location conditions and factor endowment of the city.

Each city does its part and goes its own way

The Yangtze river delta region is one of the regions enjoying the fastest development rate of industrialization in China. In addition to the differences among Shanghai, Jiangsu, Zhejiang and Anhui, there are also big differences between central and suburban areas of Shanghai, southern and northern Jiangsu, eastern and western Zhejiang, eastern and western Anhui, southern and northern anhui. In terms of the stage of industrialization, Shanghai, Hangzhou and Nanjing have entered the post-industrialization era, while Suzhou, Ningbo, Wuxi, Hefei and other cities are in the latter stage of industrialization, and many cities are still in the middle stage of industrialization. Shanghai is the most intensive city from the view of distribution of scientific and educational resources and high-end elements, followed by Nanjing, Hangzhou, Suzhou, Hefei, Ningbo and Wuxi, and then all prefecture-level cities, showing a clear hierarchical distribution. In terms of traffic conditions such as ports, railways, expressways and high-speed railways, the cities in the Yangtze river delta region are also quite different.

Shanghai has advantages in science and education resources, technology and talents, capital financing, internationalization and other aspects. It will climb up the global value chain and build a number of production service centers and high-tech industrial bases that are globally oriented and domestically oriented, laying an industrial foundation for the construction of a global city. Hangzhou, Nanjing, Hefei and other provincial capitals have regional advantages in science and education resources, technology and human resources, and will be oriented to global value chains, productive service centers serving regional economies and high-tech industrial bases. A large number of prefecture-level cities, such as southern Jiangsu cities, coastal cities of Zhejiang province and Ma’anshan-Wuhu-Tongling cities, will become manufacturing bases and regional service centers with distinct professional division of labor at different levels according to their respective geographical conditions and factor endowments. More small and medium-sized cities and small towns will give full play to their ecological advantages and become bases for ecological economy, leisure services, agricultural products processing and component processing.

Yangtze river delta economic integration will inevitably promote the layout adjustment of the different industrial chain links, achieving smooth flow of different kinds of factors and commodities, optimum setting of all kinds of talents and best utility of various cities, and let everything do its part and go its own way within the industrial chain, thus to implement the overall efficiency improvement of resource spatial allocation.