关键词: 中等收入群体, 收入极化指数, 相对分布, 非参数核密度估计

Abstract: Based on the residents' household survey micro-data of China Health and Nutrition Survey(CHNS) from 1988 to 2010, applying the nonparametric kernel density estimation method of relative distribution, we decompose the factors that affect the proportion variation of the middle-income group in this paper. Empirical results show that: on the one hand, among the factors that affect the proportion variation of the middle-income group, "Economic growth effect" is greater than "income distribution effect", and there is an increasing trend, that is, the size of the income distribution curve shift caused by economic growth is greater than the changes in the shape brought by the income allocation policy，At the same time, the short-term effect of "income distribution effect" is larger than the long-term effect. On the other hand, the lower relative polarization index is bigger than the upper relative polarization index, and the lower relative polarization index appears upward trend. It shows that, in the long term, rapid economic growth makes the criteria for the classification of middle-income group increased, while the rate of income increase in household is lower than the rate of economic growth, making the original middle-income groups fall down into the low-income group, and the proportion is greater than the group which become high-income group, and showing an increasing trend.

Key words: Middle-income Group, Income Polarization Index, Relative Distribution, Nonparametric Kernel Density Estimation