They may include complex ratios or percentages that indicate the incidence of important phenomena. Scales Value measurements are derived from the nature of the thing valued and translated onto a scale. Ordinal scales identify category and rank order. Interval scales identify rank order and have equal intervals. Addition and subtraction may be used.
Ratio scales identify rank order and interval and have an absolute zero.
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.