From a millennium to a sustainable water and sanitation development: were we there already?

The Sustainable Development Goals (SDGs) of the United Nations (UN) brought many countries closer to the best practices in several sectors. However, regarding water and sanitation services (WSS), the evolution from the original Millennium Development Goals (MDGs) is not yet understood. Therefore, analysing whether low- and middle-income nations were able to converge in terms of WSS is fundamental for policy-making. Here, we propose a benchmarking exercise aimed at assessing the performance of 123 low- and middle-income UN Member States regarding WSS development targets over the 2001–2015 period of MDG pursuance. In the end, we show that, on average, the assessed Member States were already fully convergent before the implementation of the SDGs, despite further improvements with the latter. Additionally, we show that all UN regional groupings were able to decrease not only the performance spread of their Member States, but also the gap between the best practice frontier and the worst practice frontier. Besides, the Proportion of population using an improved drinking water source was the indicator with the highest performance growth in the considered period.