A new method for group decision support based on ELECTRE
Juan Carlos Leyva-L�oopez, Eduardo Fern�aandez-Gonz�aalez *
Facultad de Ingenier�ııa, Universidad Aut�oonoma de Sinaloa, Ciudad Universitaria, Calzada de Las Americas S/N, Culiac�aan, Sinaloa,
Mexico, CP 80040, Mexico
Received 9 November 1999; accepted 9 January 2002
Group decision is usually understood as the reduction of different individual preferences on a given set to a single
collective preference. At present, there are few approaches which solve the group ranking problem with multiple criteria
in a widely acceptable way. Often, they rest on a poor heuristic which makes a decision about consensus ranking
difficult to support. This paper presents an extension of the ELECTRE III multicriteria outranking methodology to
assist a group of decision makers with different value systems to achieve a consensus on a set of possible alternatives.
Our proposal starts with N individual rankings and N corresponding valued preference functions, and uses the natural
heuristic provided by ELECTRE methodology for obtaining a fuzzy binary relation representing the collective pre-
ference. A comparison of this method with PROMETHEE II for group decision is carried out. We found that, in this
particular application, the proposed heuristic based on majority rules combined with concessions to significant mi-
norities, performs relatively better than a compensatory scheme based on a net flow weighted sum function.
� 2002 Elsevier Science B.V. All rights reserved.
Keywords: Multicriteria analysis; Group decision; Outranking methods; ELECTRE III; Genetic algorithms
People make a group decision (intra-organiza-
tional or inter-organizational) when they face a
common problem and they are all interested in its
solution. This problem may be the purchase of a
car, the acquisition of a house by a family, the de-
sign of a new product or a production planning or
to find the best location for the wastewater treat-
ment plant in a city. An important characteristic
of group decision is that all involved individuals
belong to some organization (family, firm, gov-
ernment). They may differ in their perception of the
problem and have different interests, but they are
all responsible for the organization�s well-being and
share responsibility for the implemented decision.
When a decision situation involves multiple
actors, each with different values and informa-
tional systems, the final decision will generally be
the result of an interaction between this indivi-
dual�s preferences and those of others. This inter-
action is not free of conflict, which may be due to
*Corresponding author. Tel.: +52-667-7134281; fax: +52-
E-mail addresses: email@example.com (J.C. Leyva-
L�oopez), firstname.lastname@example.org (E. Fern�aandez-Gonz�aalez).
0377-2217/03/$ - see front matter � 2002 Elsevier Science B.V. All rights reserved.
European Journal of Operational Research 148 (2003) 14-27
any of a number of factors, e.g. different ethical or
ideological beliefs, different specific objectives, or
different roles within organization. Whatever the
origin of the conflicting value systems, they will
usually affect the evolution of the decision process
in ways that were not expected at the outset (Roy,
1996; Keeney, 1992).
Group decision is usually understood as the
reduction of different individual preferences on a
given set to a single collective preference (Jelassi
et al., 1990). We will not focus on the psycholo-
gical aspects of group interactions. The main goal
of this work is the prescription of a final group
ranking from these individual preferences...
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