关键词: 城市化, 城乡人口增长率差, "S"型曲线

Abstract: This paper conducts the derivation of the urbanization curves on different hypotheses，and corrects the misunderstanding on the relationship between urbanization parameters. Under the assumption of constant urban and rural growth difference in population ( URGD) ，the time-path curve of urbanization level，velocity and acceleration would separately show a rightward“S”shape，an inverted“U”shape，and an oblique“Z”shape. Also with this constant URGD assumption，all parameters are to be set as long as two arbitrary time points of urban and rural population data are given. There is no need to turn to the linear regression between the urbanization level and time variable，and the constraint on the saturated value of urbanization level does not exist. However，under the varying URGD assumption，the urbanization curve would show certain differentiation relying on the degree of variation on URGD. With the setting of an inverted“U” shape URGD，the peak of urbanization curve would be higher and obviously shift to the left，whereas with the setting of a linear decreased URGD，the urbanization curve would appear more variation dependent upon the initial value of URGD.

Keywords: Urbanization, Urban and Rural Growth Difference in Population, "S"Shape Curve