| Abstract | Why do cities sprawl？Why is there leapfrog in the interior city? This paper focuses on the characteristic fact that land development is affected by market demand and development lag, and start from the impact of market uncertainty。Based on classical dynamic mono-centric city model, our research constructs a theoretical model which could explain the fast expansion of urban land use as well as “leapfrog sprawl”. We find that urban development density is affected by development lag, market uncertainty, and also their crossing effect. Market uncertainty has positive relationships with urban sprawl when there is a long lag. Furthermore, once taking the development ratio of interior and exterior into consideration, the improvement of uncertainty can give rise to “leapfrog sprawl”. The empirical analysis makes use of DMSP night-time light data and Landscan population data, and devises a new method to calculate urban sprawl and population density of city periphery. We tests how market uncertainty affects urban sprawl in China, the results suggest that higher degree of uncertainty does improve the urban sprawl index, which means that market uncertainty derived from economic fluctuation is also a critical cause of the form of urban spatial structure in China, so, government should take full allowance of economic fluctuation in tackling and control urban sprawl. |