To facilitate the implementation of the global indicator framework, the IAEG-SDGs categorizes the indicators into three different tiers. The tier categorization is based on their level of methodological development and the availability of data at the global level:
- Tier I indicators have established methodologies and data are regularly produced by a critical mass of countries
- Tier II indicators have established methodologies but data are not regularly produced by countries
- Tier III indicators have methodologies that are under development
Two of the SDG 6 global indicators have recently been upgraded from tier III to tier II, following a comprehensive revision of the respective methodology:
- Indicator 6.3.2 on ambient water quality – see the updated methodology
- Indicator 6.6.1 on water-related ecosystem – see the updated methodology
The revisions are based on pilot testing and an expert review in 2016, as well as lessons learned from a global roll-out in 2017.
Four of the SDG 6 global indicators are now classified as tier I, and the remaining seven indicators as tier II. This development represents a big step forward, as we are increasingly having robust methodologies in place for the global monitoring of SDG 6.