The analytic hierarchy process: can wash criteria be ignored?

We define a wash criterion as one where the decision-maker is indifferent among the alternatives when they are compared on that criterion. In view of the Belton-Gear example and other such anomalies associated with the analytic hierarchy process (AHP), we ask whether eliminating a wash criterion will affect the overall ranking of objects. In the case where there is only one level of criteria, the rank-order of objects is unaffected by leaving out a wash criterion. However, in the case where the wash criterion is a subcriterion, the rank order may be affected by leaving it out. Scope and purpose A wash criterion is defined as a criterion where the decision-maker is indifferent among the alternatives when they are compared on that criterion. We would like to think that the overall rank-order of objects would be unaffected in the case where the wash criterion is excluded. We give an example of an AHP hierarchy where this is not the case. In our view this presents another challenge to the AHP methodology. (C) 2002 Elsevier Science Ltd. All rights reserved.