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• This paper explores urban system in China and its deviations from Zipf's law. • The size distributions of Chinese cities did not follow Zipf's law until recently. • Both large and small cities were under-sized relative to the Zipf's law. • Excluding the top 10% large cities, the data fit the Zipf's law better. • The deviations rises with government interferences and decreases with market forces. How are urban residents distributed and agglomerated across different-sized cities? This question can be addressed by studying urban system or Zipf's law. Using Chinese data for the period of 1990–2017, this paper contributes to the literature by exploring the evolution of urban system, and more importantly deviations from Zipf's law. It is found that (1) The size distribution of Chinese cities, as expected, did not follow Zipf's law until very recently. Both large cities and small towns were under-sized relative to the Zipf's law, implying possible loss of agglomeration economies; (2) When the top 10% large cities are excluded, the Chinese data fit the Zipf's law better, demonstrating the adverse role of government interference in containing the growth of mega-cities; (3) By and large, the distribution has been moving closer or further away from Zipf's law, corroborating with policy directions in the relevant five-year plans of the central government; and (4) Government interferences helped enlarge while market forces helped reduce the numerical deviations of individual cities from Zipf's law. The last three analytical findings are the first in the literature since no previous studies have focused on the issue of why urban system in China does not follow Zipf's law. In particular, no earlier efforts have been made to model numerical deviations from Zipf's law, as attempted in this paper. The results appeal for removal of government interferences and furthering market-based reforms in order to reap economies of agglomeration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Accurate assessment of China's ecological environment changes in the past 20 years is important. • We used time-series NDVI data (1998–2018) to evaluate China's ecological environment change. • In one-third of China the ecological environment has improved, and in 10%, the ecological environment has deteriorated. • The Yellow River Basin is an area where the ecological environment has significantly improved. • The main reason for the deterioration in the ecological environment of the eastern coastal areas is urban expansion. The ecological environment is the foundation of human survival and development. China's ecological environment has undergone a historic transition from partial improvement to overall improvement. In this paper, long time series NDVI data (1998–2018) are used to evaluate the ecological environment change and spatiotemporal change that has taken place in China over the last 20 years, at different scales (regional, provincial, county, and grid scales). Combined with typical areas, the causes of ecological environment change are revealed. The results show that in about one-third of China, the ecological environment improved, and in 10%, the ecological environment deteriorated. Ningxia, Shaanxi, Shanxi, Guizhou, and Guangxi are the provinces in which the improvement of the ecological environment is most pronounced. However, the ecological environments with vegetation as the core in Shanghai and Jiangsu Province have deteriorated significantly. The areas with the fastest improvement in their ecological environment are those with precipitation of 200–600 mm. The Yellow River Basin is an area where the ecological environment has significantly improved. Forestry projects and the development of oasis agriculture effectively promote the improvement of the ecological environment. In the past 20 years, the main reason for the degradation of the ecological environment in eastern coastal areas is urban expansion. China should continue to strengthen its overall layout of forestry projects and improve its ecological environment. When planning its ecological construction, China should fully consider the associated physical and geographical conditions, and adjust measures to local conditions accordingly. China should coordinate the relationship between development and protection and avoid the "pie spread" expansion witnessed in eastern coastal areas. [ABSTRACT FROM AUTHOR]