A Repeatable Multi-Criteria Decision Model for Social Housing Asset Intervention Decisions

This report describes a case study where a multi criteria decision model is used to make decisions regarding asset interventions for four social housing complexes, similar in terms of issues and possible interventions, at Christchurch City Council. The value judgements from the decision makers and their advisors that were necessary for creating the decision model were elicited through three workshops; selecting aspects, weighting and rating and lastly reviewing the output. An analysis performed shows that the decision model is logically consistent and does not suffer from the rank reversal phenomenon. The validation of the model also included creating four individual decision models, one for each social housing complex, comparing the results of applying the joint model and the individual models, and revisiting and reconsidering the value judgments made in the different models when discrepancies were found. This included utility difference analysis and asking trade-off questions to the decision makers. Part of the validation was also to get acceptance of the output of the joint model from the social housing team. Applying the decision model on the four social housing complexes and receiving an output which is accepted by the social housing team suggests that the aggregated model can be used for future decision problems of the same kind, provided that they are within the set level ranges of the aspects. Since the decision model is transparent in terms of which values or priorities have been applied and which prerequisites must be met in order to apply the model to future decisions, it is possible to use the decision model as a ‘live model’ with adjustment being made to it when required