Methods of Measuring and Decomposing the Income Gap： A Survey

In this study, we classify the income gap into the total income gap and the inter-group income gap depending on the subjects of study. Measurement and decomposition methods are discussed at three levels： income inequality, polarization, and the inter-group income gap. While income inequality focuses on description of the overall income gap, polarization aims to examine the phenomenon of the ＂clustering effect＂ in income distribution, for which the measurement indexes used can be broadly divided into bi-polarization and multi-polarization indexes. The Shapley decomposition method and decomposition of the distribution of inter- group income differences are cutting edge techniques for the decomposition of the income gap. We also stress the applicability and relevance of income gap measurement indexes and decomposition methods, to facilitate selection of the most appropriate methods for more accurate detection of the causes of the income gap.

本文按研究对象将收入差距划分为总体收入差距和组群收入差距两大类，从收入不平等、极化和组群收入差距三个层面梳理了收入差距的测度及其分解方法。其中，收入不平等侧重于对总体收入差距的刻画；极化着眼于收入分布中的“聚集”或“扎堆”现象，其衡量指标大体上可分为两极分化测度指标和多极分化测度指标。在收入差距的分解上，Shapley分解和组群收入差距的分布分解方法都是较为前沿的研究领域。文章还强调了各种收入差距衡量指标或分解方法的适用性和针对性，以便有的放矢地选用合适的相关指标和方法，更精准地探寻收入差距的成因。