On aggregating multiple indicators into a single metric for sustainability

In sustainability analysis of multidimensional states of a system, it is required to establish the relative superiority of one of the states. Particularly when a finite number of quantitative metrics is used to characterize the system, the values of the metrics among the states can exhibit increasing and decreasing trends at the same time, creating difficulty in clearly preferring one to the other. Sometimes, unequal weighting factors are ascribed to metrics to show the relative importance of the metrics, further complicating the comparison. It has been deemed desirable to consolidate all the usable metrics into one aggregate metric to make this comparison easier. Such an attempt is provided here by expressing the aggregate metric as the geometric mean of the ratios of the individual metrics for pair-wise comparisons. This computation was applied to previously reported evaluations of processes with a finite number of metrics. The method also reveals the sensitivity of the aggregate metric to the individual metrics and to the weighting factors.