At this stage, the goal is to find the alternative that offers the best balance across the objectives, in consideration of the diverse values and perspectives of the affected parties. This step involves thinking and talking about difficult value-based trade-offs, clarifying preferences and the reasons for those preferences, and seeking a solution that can be broadly supported.
When we use the term ”trade-offs”, we simply mean the situation where there is at least one pro and at least one con between at least two alternatives. Before we can say that one is “better” than the other we have to make a judgment call based on our values. In a supermarket, if one apple is fresh and costs $1, but another is less fresh and costs $0.50, and all else is equal, which is best? The answer is, it depends – on how important the difference in freshness and $0.50 are to whoever you’re asking. Reasonable people may disagree on which apple is best given this trade-off: there’s no correct answer.
Essentially, SDM focuses people on key trade-offs across alternatives in an effort to find an alternative that everyone can support. The emphasis on trade-offs may feel unusual, but it really is at the heart of good decision making. If a group is serious about trying to find a mutually acceptable outcome, a focus on trade-offs helps to:
- Identify alternatives that are simply not efficient (that is, they are sub-optimal in that they can be improved in one or more respects without causing a decline in others)
- Provide insight on new or hybrid alternatives
- Learn the limits of the irreducible trade-offs that exist between alternatives (where there’s no way to improve the performance of X performance measure without also reducing the performance of Y or Z)
- Prepare the basis for difficult and meaningful conversations about finding the alternative with the “best” balance of performance given the constraints of the decision context.
A good deliberative trade-off process emphasizes respectful reason-giving, reflection and learning. Structuring tools and professional facilitation can help to expose errors of logic and reasoning, promote co-learning, build a broader appreciation of the perspectives of others, and improve the consistency and transparency of choices.
So how do we do it? A first step in evaluating trade-offs is to try to simplify the consequence table by checking for insensitivity and dominance. That is, by hiding performance measures that don’t vary across the whole range of alternatives, and removing any alternatives that are fully out-performed by another.
Next, it can be helpful to walk participants through a series of paired comparisons. This is a deliberative approach in which attention is drawn to the trade-offs (the pros and cons) between any two of the alternatives, and the conversation is focused on clarifying preferences – can we agree that one alternative is “better” than another? Sometimes this process leads directly to the identification of a preferred alternative. In other cases, new alternatives are suggested through discussion which may result in another round of evaluation.
If the decision is particularly complex or there are challenges in reaching a broadly supported decision, a variety of methods from the decision sciences are available to support deliberations. For example, it may be useful to use formal preference assessment methods for explicitly weighting the measures and deriving scores and ranks for the alternatives. In groups who share similar values, it might be possible to agree on a set of weights for the measures, and use calculated performance scores to quantitatively rank the alternatives. In many groups however, people will have such diverse values that agreeing on or averaging weights is neither possible nor useful. In this case, some practitioners use preference assessment methods not as a way to calculate the best alternative, but rather as a way to support and inform the deliberative process. For example, the results can help to identify and challenge hidden biases, to clarify sources of agreement and disagreement (do participants disagree about facts or values, for example), and to focus and structure dialogue in ways that support collaborative, interest-based decision making.
Sometimes this deliberative exploration of trade-offs leads seamlessly to a preferred alternative. Other times, it leads to the development of new and better alternatives, and another round of evaluation occurs.