Mobility and Mobility Measures

Abstract

We examine whether mobility measures appropriately represent changes in individual status, like income or ranks. We suggest three elementary principles for mobility comparisons and show that many commonly used indices violate one or more of them. These principles are used to characterise two classes of measures that have a natural interpretation in terms of distributional analysis. Class-1 measures are based on the summation of power functions of individual status levels and have connections with generalised-entropy and Kolm inequality measures. Class-2 measures are based on the weighted aggregation of individual status changes and have connections with (extended) Gini inequality measures.

Keywords: income mobility, rank mobility, measurement, axiomatic approach

JEL Classification: C6, D6, I3