From Sprawl To Multi-center Agglomeration

Area of Built District and population of Chinese cities increased rapidly in the past 20 years and the phenomenon of urban sprawl is significant.In this process,city sub-centers had been built and the mono-center sprawl evolved into multi-center agglomeration.The formation of multi-center agglomeration optimizes the urban spatial structure by helping residents to work near sub-centers and easing the problems of decreasing density and increasing commuting cost,so that urban productivity improves.This paper analyzes the urban mono-center sprawl model and finds that the increase of income of the residents and the decrease of commuting cost can cause city expansion.By extending the model to multi-center situation,we also find the conditions of sub-center formation in urban sprawl.A higher proportion of the export products,more expensive land price of the city center or preferential policies may increase the probability of the formation of urban sub-centers,which leads to the development multi-center structure and multi-center agglomeration.According to the historical data of Chinese cities,urban scale growth and progression of traffic technology makes cities to sprawl,and the development of the manufacturing industry and the upgrade of industrial structure promotes manufacturing relocation.Last but not least,local government's policy is also a guide of multi-center agglomeration.The development of multi-center spatial structure of cities of eastern China is better than cities of central China both from the evolution process and current situation,and central cities are better than western cities.This paper argues that the sprawl may affect urban productivity through the density effect,scale effect and land-labor substitution effect.The agglomeration of manufacturing sub-centers and producer service industry and the interaction between two sectors has an important role in urban productivity.The empirical analysis shows that:(1)the density efFect and the scale effect of the sprawl will partially balance out,and the influence of the change of the land-labor factor substitution relationship is not significant,so the total effect of the sprawl on the urban productivity is not obvious.The increase of employment density and employment scale are not conducive to the improvement of manufacturing productivity,but may have a positive impact on service industry.(2)Multi-center agglomeration has a positive effect on urban productivity,and the most obvious effect is the interaction between the manufacturing industry of sub-centers and the producer service indusrtry of city center.Although the agglomeration effect of the producer service industry has not been universally worked due to the low development level of the producer service industry,but it has begun to promote the urban production efficiency in cities with multi-center structure.The agglomeration effect of manufacturing sub-centers is particularly prominent for the productivity of transitional cities,while it's weakening in multi-center cities with the maturity of the manufacturing industry.