Decomposing socioeconomic health inequalities

Excerpt

This Hints & Kinks paper describes a technique enabling quantification of the contributions of determinants to socioeconomic inequality in health. This technique, differing from an analysis investigating the determinants of average health levels, has received considerable attention from health economists (van Doorslaer and Gerdtham 2003; van Doorslaer and Jones 2003; van Doorslaer et al. 2004; Wagstaff et al. 2003) but only more recently from epidemiologists as well (Harper and Lynch 2007; Lynch 2006; Hosseinpoor et al. 2006). This paper employs the relative concentration index (RCI), described in Konings et al. (2009), to summarize relative inequality across the entire socioeconomic distribution. The RCI of a continuous health outcome y results from a relative concentration curve, which graphs on the x-axis the cumulative percentage of the sample, ranked by an indicator of socioeconomic position such as education or income beginning with the poorest. The y-axis then indicates the cumulative percentage of the health outcome corresponding to each cumulative percentage of the distribution of the socioeconomic indicator. Figure 1 provides an example of a concentration curve, where the health variable is childhood malnutrition in Ghana in 2003. It shows that the level of malnutrition accumulates faster among the poor than among the better-off because the line is above the diagonal. The RCI is defined as twice the area between the concentration curve and the line of equality (the 45° diagonal from the bottom-left corner to the top-right). Details on how to compute the RCI can be found in Konings et al. (2009).

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