Equity in water and sanitation: developing an index to measure progressive realization of the human right.

We developed an index to measure progressive realization for the human right to water and sanitation. While in this study we demonstrate its application to the non-discrimination and equality component for water, the conceptual approach of the index can be used for all the different components of the human right. The index was composed of one structural, one process, and two outcome indicators and is bound between -1 and 1, where negative values indicate regression and positive values indicate progressive realization. For individual structural and process indicators, only discrete values such as -1, -0.5, 0, 0.5, and 1 were allowed. For the outcome indicators, any value between -1 and 1 was possible, and a State's progress was evaluated using rates of change. To create an index that would allow for fair comparisons between States and across time, these rates of change were compared to benchmarked rates, which reflect the maximum rates a State can achieve. Using this approach, we calculated the index score for 56 States in 2010 for which adequate data were available and demonstrated that these index scores were not dependent on factors such as achieved level of coverage or gross national income. The proposed index differs from existing measures of inequality as it measures rate of change and not level of achievement, and thus addresses the principle of progressive realization that is fundamental to human rights.