4.7 Cross-indicator score aggregation

One value of the Report Card is that indicators were normalized to a common scoring scale, 0 (poor condition) to 100 (good condition), where good and poor conditions were defined for each indicator. For goals and objectives that have more than one indicator, it is then possible to combine the indicator scores into an overall score for that goal or objective (see Executive Summary). The steps for doing this included: 1) analyzing individual indicators, 2) transforming indicator values to a single scoring scale, 3) determining the relative importance of each indicator (by default we assumed each was equally important), and 4) averaging the scores for indicators within a goal or objective. In the case of (4), averaging is one way that the scores could be used. Another possibility would be to selected the lowest score in order to point out the conditions that might need the most attention, or to weight the scores according to a social or management ranking of indicator importance.

Carrying out this type of score aggregation is appropriate for a decision-support device like the Report Card, which is intended to provide a quantitative estimate of how well conditions are performing relative to goals. The scores may seem less relevant to an ecological or economic model where the base parameters units (e.g., tons of nitrogen, $) may be more useful. However, there are few quantitative modeling approaches that can use multiple parameters in their native units to reflect conditions in complex systems like watersheds. It is possible that the normalization approach used for the Report Card can be used to quantitatively reflect conditions of and interactions among watershed components.