Selection and valuation of criteria in decision-making for improvements in
v/Dag Bertelsen, SINTEF
This abstract does not, in fact, respond to the four key questions: background, methods,
results, conclusions. Nevertheless, it should give an good impression of the content in a
complete paper, which I hope will be of interest for the conference.
The aim of all decision-making, for companies as well as for the society as a whole, is to
choose the best among a number of alternative solutions. However, what is “the best” will
often depend on a judgement of the importance of different aspects of the alternatives.
Diversion in judgement among the decision-makers will lead to different conclusions as to
which solution is the best. On the other hand, lack of consistency and completeness in the set
of aspects included in the decision basis will normally lead to questionable decisions. Lack of
consciousness in the assessment of different aspects and solutions may also result in illogical
For some decisions it is normal or acceptable to calculate and present all the relevant aspects
in a common monetary unit. This will be the case when comparing two different ways of
constructing a bridge. However, even then you have to ensure that all aspects are included and
no aspect is added more than once. If the reinforcement for a bridge is calculated as a separate
element, it is not to be included for each beam or pillar. If all principles for economic
calculations have been followed, the total costs will be a correct basis for decisions.
Often it is neither acceptable nor possible to calculate in monetary units all the aspects in
question, especially when health, environment and security aspects are involved. Then it will
be necessary to include into the decision process several aspects quantified in different units.
This results in a so-called multi-criteria decision-making.
It is much more challenging to secure a consistent decision basis for a multi-criteria situation
than for a single-criteria situation. Unfortunately, this is often disregarded both by the
decision-supporters and by the decision-makers.
A simple example of a multi-criteria decision situation exist when the number of injured
persons in different age groups is reduced by some improvements in the system in question,
for instance in the water supply system or in the transport system. Everyone realise that the
decision basis will be wrong if there are overlaps or gaps between the age groups when
presented for the decision-makers. This is as obvious as mistakes in calculation of
construction costs for a bridge. It is crucial for a rational decision that the decision basis
comprises a mutually consistent set of criteria.
Normally, the development of a consistent set of decision criteria will be quite more
complicated than illustrated above. Of course decomposition of benefits into subgroups has to
be consistent. It is quite more difficult to secure that the decision criteria is selected from the
same level in a cause-effect model for the system in question, especially in cases where no
formal cause-effect model is established. Then it is every reason to examine the criteria in the
decision basis before presenting them for the stakeholders and decision-makers. Without
some sort of a cause-effect model it will be almost impossible to secure a consistent set of
decision criteria. This has to be exemplified, here from the transport sector.
New link in the
Improvement of road
Expanding road width
Figure 1: The lower part of a simplified cause-effect model for improvements in a road
The red boxes at the top of figure 1 may be regarded as decision-criteria. The arrows represent
mathematical or other relationships between the various elements necessary to determine
quantities for each criterion. By using this model both for the existing and for the improved
transport system, the benefits can be calculated for various improvements.
Some people may consider accident rate, travel speed or road geometry as relevant decision
criteria in addition to, or instead of the criteria in the red boxes. Or they may consider health
impacts to be added to the red box criteria and presented for the decision-makers. How should
decision-supporters decide upon such questions?
Figure 2: Idealised representation of the upper part of a cause-effect model
The decision-makers have to judge the relative importance of the decision criteria to come to
conclusions. Which considerations should it be rational for them to make in this connection?
They should be expected to have a superior aim and therefore an opinion on the contribution
of each criterion to this aim. In fact, this represents an upper part of the cause-effect model
shown in figure 2.
The upper part of the cause-effect model is significantly more dependent on personal opinions
than the lower part shown in figure 2. The purple box on the top raises the question weather
life quality for animal should be included, and even weather there is a life after death. These
are examples of aspects which politicians are supposed to take into account when making
Noise as well as pollution and traffic accidents form, according to figure 2, the basis for
determination of health impacts. If health impacts from noise, pollution and accidents are
added to the red box decision criteria, then the decision-makers are invited to double count
these health aspects.
So, the red box criteria in figure 1 and 2 may be an appropriate set of decision-criteria for
situations covered by this cause-effect model. There will definitively also exist other sets of
decision-criteria which will satisfy the consistency requirements.
In figure 3 the whole rectangle
represents total benefits for a specific
decision situation. Each of the
coloured areas represents specific
decision criteria. In the left part of
the figure the total area is covered
and there is no overlap between any
of the criteria. In the right part there
are both overlap between many of
the criteria and parts of the area are
Figure 3: Illustration of one formally right and one wrong set of decision criteria
This is even more complicated since there will often exist a great variety of sets of decisioncriteria
which will not fulfil the consistency requirements. The decision-supporters are
expected to be aware of this and to avoid inconsistent sets of criteria in the decision basis.
Thus a main duty for decision-supporters is to select a set of criteria which give the
stakeholders and decision-makers a good basis for personal judgements and conclusions. It
must be admitted that this is not always paid the attention it should. In fact, the decisionsupporters
often ask the decision-makers to tell which set of criteria to be used, and then
regard this as a proper set of decision criteria.