SDG Indicators are characterised by heterogeneous measurement units. This makes it difficult to compare them as well as produce aggregate indicators. Four main steps can be identified to bring all SDG Indicators to a common metrics:
- identification of the measurement unit (money, shares, tons, etc.);
- definition of the range within which past and projected indicator values fall;
- benchmarking, which is set at max-min thresholds derived from policy targets, literature review or current observations;
- normalization of values in the common range [0, 100].
It is worth noting that, according to their nature, indicators can have either positive (the higher the better) or negative (the higher the worse) interpretations. The normalization steps reconcile these different paths by uniformly applying the convention of the higher the better (a score of 100 coincides with a fully sustainable performance).