The lack of access to water and sanitation services (WSS) of a considerable share of the world population has been challenging the international community for decades. The proposal of the Millennium Development Goals and, later on, the Sustainable Development Goals (SDGs) by the United Nations (UN) intended to act as a blueprint to achieve a more equitable future for all and, in the case of WSS, “Ensure the availability and sustainable management of water and sanitation for all” (SDG 6). However, the current global pandemic further emphasised the importance of WSS, given the increasing asymmetries faced by billions worldwide, and the gaps between high-income and low- and middle-income nations. For this reason, understanding whether low- and middle-income countries have been approximating towards or deviating from the SDG 6 is crucial to derive and communicate key information for the sake of improved public governance and political decision-making. In this paper, we extend a state-of-the-art methodology based on data envelopment analysis for assessing the convergence of the low- and middle-income UN Member States regarding the SDG 6 between 2016 and 2017. We find that, on average, not only did the Member States converge by decreasing the performance spread and the gap between the best and worst practice frontiers, but also the Level of water stress: freshwater withdrawal as a proportion of available freshwater resources was the indicator in which the majority exhibited the worst performances. In the end, we derive possible policy implications, which, as our results show, are aligned with the recent UN reports on the subject.

数十年来，世界上相当大一部分人口无法获得水和卫生服务 (WSS) 一直是国际社会面临的挑战。联合国 (UN) 提出的千年发展目标以及后来的可持续发展目标 (SDG) 旨在作为实现所有人更公平未来的蓝图，就 WSS 而言，“确保人人享有水和卫生设施的可用性和可持续管理”（可持续发展目标 6）。然而，鉴于全球数十亿人面临日益严重的不对称以及高收入与中低收入国家之间的差距，当前的全球大流行进一步强调了 WSS 的重要性。为此原因，了解低收入和中等收入国家是接近还是偏离可持续发展目标 6，对于获取和交流关键信息以改善公共治理和政治决策至关重要。在本文中，我们扩展了一种基于数据包络分析的最先进方法，用于评估 2016 年至 2017 年间联合国中低收入成员国在可持续发展目标 6 方面的趋同性。我们发现，平均而言，不仅成员国通过减少绩效差异和最佳和最差实践前沿之间的差距而趋于一致，而且水资源压力水平：淡水抽取量占可用淡水资源的比例是大多数表现最差的指标。最后，我们得出可能的政策影响，正如我们的结果所示，这与联合国最近关于该主题的报告一致。