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A Method for Decision Making using Sustainability Indicators
Citation:
SMITH, R. L. AND G. J. Ruiz-Mercado. A Method for Decision Making using Sustainability Indicators. CLEAN TECHNOLOGIES AND ENVIRONMENTAL POLICY. Springer Berlin-Heidelberg, , Germany, 16(4):749-755, (2014).
Impact/Purpose:
To inform the public.
Description:
Calculations aimed at representing the thought process of decision makers are common within multi-objective decision support tools. These calculations that mathematically describe preferences most often combine various utility scores (i.e., abilities to satisfy desires) with weighting factors for each desire or objective onto a single scale to allow a ranking of alternatives. However, seldom are the tradeoffs implied in creating a single scale for multiple objectives described explicitly. This paper illustrates how choices for combining utility scores are in fact a statement of equivalence between the weighted utility scores of these objectives, even if the choice of weighting factors was intended to be value free. While one might, for example, attempt to avoid value judgments by making the weighting factor for economics the same as those for energy use and/or the environment (or various individual environmental indicators), this paper will show that in choosing “equal weighting” that specific value judgments have nevertheless been made. In addition, the relationships between objectives can be rewritten as a series of equations (i.e., relationships) for the weighting factors. Depending on the number of relationships specified, the weighting factors can be underdetermined, unique, or overdetermined. Calculations using the singular value decomposition method can be used to determine the weighting factors for each of these situations, allowing for explicit representations of the implied tradeoffs for decision makers. Finally, a simple but powerful method for calculating total utility using the marginal rates of substitution between utility scores rather than weighting factors is presented. Utility calculations based on the more intuitive marginal rates of substitution can then be used to evaluate various alternatives. The decision maker can see the effects of changing the marginal rates of substitution (i.e., utility tradeoffs) and attributes (i.e., design or operating parameter) values for alternatives. While an example from chemical production for terephthalic acid is presented, the methods shown are generally applicable.
