Population Migration at Different Administrative Levels in Sichuan Province
分析了四川省镇、县、市三个行政级别的人口时空变化，发现人口集中在成都平原及东北、南部经济区，城市人口比例高但层级结构不完善，不同经济区各级人口增长模式各异。
As the fourth largest population province in China, Sichuan province has great differences in natural and economic condition, which influence the growth of population at different administrative levels. This paper analyzes the temporal and spatial variation of population in three administrative levels- town, county and city. The results show that:(1) Settlements are concentrated in the Chengdu Plain, the Northeastern and Southern economic zone. From the perspective of different administrative levels, the proportion of population in cities is large, but the grades of population's hierarchical structure are low and imperfect; the population scale in counties is mainly 100 000-200 000 and 20 000-50000, demonstrating the population pattern of greater in the east than in the west; the population scale in towns is below 10000.(2) Population proportion ranks the first in cities, the second in towns, and the third in county in the Chengdu Plain,the Northeastern and Southern economic zones. While the situation is on the contrary in Pan- Xi and Western economic zones, where it's the countries that have the largest population proportion. From the comparison of the early and late proportion, cities in the Chengdu Plain economic zone grow fastest, and towns grow faster than counties; towns and counties in the Northeastern and Southern economic zones have large effects on population agglomeration; counties in the Pan- Xi economic zone are attractive; in the Western economic zone the population proportion has been increasing in towns but decreasing in counties.(3) The distribution of towns shows inverted U-shape in plain and hilly areas. The more complex the terrain is, the more balanced the distribution of towns is; The population growth is fluctuating in different types of counties. In general, the growth interval is greater when the hypsography is smaller.