Group decision as a twice multicriteria optimum problem

This paper studies the problem of aggregation of preferences, preserving the multicriteria nature of the individual decision process. The resulting group decision problem is in effect a twice multicriteria optimum problem. The paper gives a structural theory for the efficient set of this optimum problem. Moreover, on the basis of this theory it studies the relationships between optimality, consensus and evaluation. The paper confirms the pathological nature of aggregation of preferences, but in a new setting and with a different meaning.