Decomposing poverty changes into vertical and horizontal components

Variations in aggregate poverty indices can be due to differences in average poverty intensity, to changes in the welfare distances between those poor of initially unequal welfare status and/or to emerging disparities in welfare among those poor of initially similar welfare status. This note uses a general cost‐of‐inequality approach that decomposes the total change in poverty into a sum of indices of each of these three components. This decomposition can serve inter alia to integrate horizontal and vertical equity criteria in the poverty alleviation assessment of social and economic programmes. The use of these measures is briefly illustrated using Tunisian data.