Inequality in water supply in India: an assessment using the Gini and Theil indices

Provision of drinking water is considered to be an essential public service. Ensuring adequate water supply remains a challenge in Indian cities that are experiencing rapid growth and often exhibit a mismatch between increasing demands and inadequate supply infrastructure. This study quantifies the existing inequality in water supply within Indian cities through Lorenz curve, Gini coefficient as well as Theil indices. Two types of Theil indices are estimated to gain different perspectives: water supply and population-weighted. Both the Theil indices are disaggregated, according to economic and regional categorisation of the cities, to explore the within- and between-group inequality. The water supply and population-weighted Theil indices provide different outlook of the inequality amongst the cities. But the population-weighted index is often better and pragmatic. Further, the inequality in access to tap water in India is studied by estimating modified Lorenz curves and Theil indices. Again, the Theil indices are decomposed into within and between components according to economic and regional grouping of states. The results suggest that there is disparity in supply of water in India, and infrastructure has to be boosted to meet the growing demand. This study is a step towards quantification of water supply inequality. The approach used in the study can contribute to monitoring of water supply equity as well as in formulating sustainable and equitable water policies.