Relative Index of Inequality and Slope Index of Inequality: A Structured Regression Framework for Estimation

Abstract

Background: The relative index of inequality and the slope index of inequality are the two major indices used in epidemiologic studies for the measurement of socioeconomic inequalities in health. Yet the current definitions of these indices are not adapted to their main purpose, which is to provide summary measures of the linear association between socioeconomic status and health in a way that enables valid between-population comparisons. The lack of appropriate definitions has dissuaded the application of suitable regression methods for estimating the slope index of inequality. Methods: We suggest formally defining the relative and slope indices of inequality as so-called least false parame..