Measuring the magnitude of socio-economic inequalities in health: an overview of available measures illustrated with two examples from Europe

In this paper we review the available summary measures for the magnitude of socio-economic inequalities in health. Measures which have been used differ in a number of important respects, including (1) the measurement of "relative" or "absolute" differences; (2) the measurement of an "effect" of lower socio-economic status, or of the "total impact" of socio-economic inequalities in health upon the health status of the population; (3) simple versus sophisticated measurement techniques. Based on this analysis of summary measures which have previously been applied, eight different classes of summary measures can be distinguished. Because measures of "total impact" can be further subdivided on the basis of their underlying assumptions, we finally arrive at 12 types of summary measure. Each of these has its merits, and choice of a particular type of summary measure will depend partly on technical considerations, partly on one's perspective on socio-economic inequalities in health. In practice, it will often be useful to compare the results of several summary measures. These principles are illustrated with two examples: one on trends in the magnitude of inequalities in mortality by occupational class in Finland, and one on trends in the magnitude of inequalities in self-reported morbidity by level of education in the Netherlands