中文摘要：

现有中等收入人口规模的统计测度方法,要么依赖于中等收入界限的划分,要么存在不能完全排序的情况,具有一定局限性。为此,本文考虑了三种不同方案,对M-曲线进行积分,构造出新指数,用于揭示中等收入人口规模变动规律。研究表明：这一新指数是一个综合指数,既无需提供中等收入界限,又能够实现完全排序,可以很好地用于中等收入人口规模的历史评价与地区比较。最后,将新指数应用于中国城镇居民分组数据进行实证研究,发现2001-2006年,中等收入人口规模大幅度缩小,而在2006-2011年,中等收入人口规模有所增加。

英文摘要：

The existing approaches have two main disadvantages. Some methods depend on middle income demarcation, and some methods can only get partial ordering, not complete ordering. To tackle these two issues, we construct a new index to track variation of middle income population size through integrating M-curve by three different weighting schemes. As a composite index, the new index can be used for historical evaluation and regional comparison of middle income population size, which does not depend on middle income demarcation and can get complete ordering. At last, the index is applied to integrated data of Chinese urban residents. The empirical results show that the population size of middle income group in China decreased sharply from 2001 to 2006, and enlarged from 2006 to 2011.