Abstract
In the present decade, the following three major developments in the theory of inequality measure of size distribution of income have been undergone: (1) the choice of inequality measures, (2) utilization of extraneous information, and (3) statistical treatments. The focal points in the first one are to interpret inequality measure as a social welfare function and to establish a relationship between inequality measure and traditional Lorenz curve. The second aspect has appeared in connection with development of computer which facilitates largescale statistical surveys. They permit the use of various information associatedwith income and stimulate a number of decompositions of inequality measures. Statistical problems emerging from the use of grouped data are raised and now being tackled. This survey aims to review these new theoretical results, particularly with economic application in mind. Their historical notes are also added.
