Why a set of sustainability indicators, and not a composite indicator?

The great advantage of a composite indicator is that it is a powerful means of communication. Because a development can be expressed in just one number, it is easy to interpret. The disadvantage of a composite index is that by definition it is built up from underlying sub-indicators, that are weighted and thus valued. However, sustainability is a multi-dimensional concept and cannot be expressed in one number. None of the composite indices developed up to now comprises all aspects of sustainability. Because of these disadvantages, we decided to analyse the sustainability of Dutch society using a set of indicators. Many other European countries also analyse sustainability in this way.
An extensive overview of composite indicators and indicator sets is presented in:

Kulig, A.B., H. Kolfoort, and R. Hoekstra, 2010. ‘The case of the hybrid capital approach for the measurement of the welfare and sustainability’. Ecological Indicators 10 (2010), pp. 118-128.