The graph is from the paper "Using Census Data to Explore the Spatial Distribution of Human Development" by Iñaki Permanyer. A draft is here and it is published in World Development (June 2013). The abstract:
The human development index (HDI) has been criticized for not incorporating distributional issues. We propose using census data to construct a municipal-based HDI that allows exploring the distribution of human development with unprecedented geographical coverage and detail. Moreover, we present a new methodology that allows decomposing overall human development inequality according to the contribution of its subcomponents. We illustrate our methodology for Mexico’s last three census rounds. Municipal-based human development has increased over time and inequality between municipalities has decreased. The wealth component has increasingly accounted for most of the existing inequality in human development during the last twenty years.