This allows for more complex mathematical operations. The more complex scales may be mapped onto the simpler but not vice versa. In assessing sustainability we normally use ordinal or interval scales. The best way to aggregate this type of measurement at community level is through discussion to arrive at a consensus. This reveals both the nature of the value judgements, and who makes them.
Aggregation involves subjective judgement, whether arbitrary or based on experience.
The danger in using quantitative indicators and aggregate measures is the assumption of their objectivity. We must assume that decision-making and assignment of value are inherently political, involving multiple biases or areas of interest, and the interaction of numerous groups or organisations with different goals. Decision-making needs to be perceived as an inherently argumentative process. If indicators are being selected for use with the Barometer of Sustainability, discuss whether all of the issues should be used in coming to an overall judgement about how the human system and ecosystem are doing. If some are more important than others, use pair-wise ranking.