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Voting Systems and Multi-Criteria Optimization Models in Participative Decision Making

B. Srdjevic1*, O. Cukaliev2, V. Tanaskovic2, Z. Srdjevic1, Bosko Blagojevic1

1Faculty of Agriculture, University of Novi Sad, Trg D. Obradovica 2, 21000 Novi Sad, SERBIA 2Faculty for Agricultural Sciences and Food, Ss. Cyril and Methodius University, Blvd. Aleksandar

Makedonski bb., 1000 Skopje, MACEDONIA

bojans@polj.uns.ac.rs Abstract The paper presents overview of several voting systems from the Social Choice Theory and possibilities for their combining with the multi-criteria optimization methods (and AHP- analytic hierarchy process in particular) to aid the decision making processes in assemblies of water users associations in Serbia and Macedonia. Preferential and non-preferential voting systems are applied along with the AHP within unique SCT+AHP participatory decision making framework to assess five annual action plans for given fiscal year in small assembly. A decision making body is an assembly constituted of 28 delegates representing eight different interest parties, from large and small irrigators to independent experts and NGOs. A case study example is adapted from several research reports completed in recent years in Vojvodina Province of Serbia. The results demonstrate what may occur if different group decision making techniques apply to the same problem. The paper traces some important elements of future research agenda. Keywords: water users associations, group decision making, voting methods, AHP Introduction There are many important issues related to the decision making processes related to water resources planning and management. In this paper we concentrate on two classes of participatory decision making models applicable in within water users’ association (WUA), that is, its assembly where decisions are to be made by delegates from different interest groups (stakeholders) (1). The organizational and internal structure of the WUA, normative documents, involved administrative personnel, and water users are the core part of the WUA. The latter are dominantly small and medium properties of farmers (say 5-30 hectares), but also large irrigators operating on hundreds and thousands of hectares of owned or rented land. One of the essential factors for proper irrigation management is to include the farmers (final users) in the water users association (2).Except core part of the WUA, however, there are other interests and impacts such as those related to political influences, the actions of NGO representatives, involvement of ‘in-situ municipalities’, inspection services, or the advisory role of independent (mainly academic) experts. Depending on the adopted organizational scheme and established statutory rights and obligations, the decision process at various stages can be organized in different ways. Essential is how to assure fair process and reduce the negative manipulation of important information and data, and how to motivate decision-makers or their interest groups to competently participate in creating the process and derive at a valuable final decision(s). Here we discuss one possible scenario of implementing specific decision making tools that can provide a competent statement and assessment of a decision problem in the WUA, enable the evaluation of decision elements (criteria and alternatives), and assure the derivation of the final group decision based on the aggregation of individual decisions ‘delegated’ by various interest groups within and outside the WUA. Various choice procedures are introduced in advanced studies of agricultural policies, water systems control and general management of natural resources. In particular, voting systems and their linking with multi-criteria models is elaborated in modern times in attempt to identify the most convenient way of their use in a participative decision making. Social choice theory (SCT) and its voting systems such as plurality voting, the Borda count, pairwise comparison voting, or approval voting are most commonly

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used. On the other side, multi-criteria decision making methods (MCDM) is a common name for various classes of methods such as utility methods, outranking methods or ideal-point methods, to mention but a few. Neither of aforementioned systems and methods, individually and jointly, is evidenced at applicative level in group decision making in responsible institutions in Serbia and Macedonia that gather interests of various social, political, environmental and other users groups. After introducing several typical SCT systems and one representative MCDM method, we present an illustrative case example of decision making in a small water users association, that is in its decision making body – an assembly. Underlying assumption is that association is experiencing conflicts of interests of involved parties (interest groups/stakeholders) in study area within Vojvodina Province of Serbia (Figure 1) (3), characterized by limited water availability and significant water demands. Similar situation is recognized in parts of Macedonia (4) and therefore framework for the two states is common. The decision making body has to meet two essential tasks. The first one is to organize the process of consistent identification of common goals, objectives and several annual action plans as decision alternatives, and in turn perform multi-criteria analysis to derive plans’ preference lists for each participating interest group. The second one is to apply proper voting scheme to derive final solution – the final ordering of annual plans. We discuss issues related to the problem identification, options and models for multi-criteria analysis and application of four possible voting schemes. We also point to possibilities of majorization or manipulation of the decision process. Discussion is aimed toward identification of procedures that can help to bridge the gap between theory and real-life decision making.

Figure 1. Serbia (and Vojvodina Province in the northern part) and Macedonia Voting systems and multi-criteria decision making models In solving the group decision problems one of key issues is to determine which methodology should be used and to foreseen the outcome that can be expected. If the Social Choice Theory, and its voting systems are to be used, an important issues are fairness and manipulation of the voting system used. Various authors argue that none of the voting methods is immune to violation from at least one of the commonly used fairness criteria. To preserve the homogeneity of the decision process, they advocate clustering of individuals within a group before conducting the election process; an argument is that in this way a democratic procedure is also preserved (5-7). On the other hand, the multi-criteria decision making (MCDM) applications must respect the size of a group because philosophy behind the multi-criteria methods rely on an assumption that the homogeneity principle is valid. Several authors argue that in larger groups this assumption may be

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violated and advocate a group clustering based on similarities in decision making preferences (8) wherever the group is of an intermediate or large size (9). However, even in subgroups some of the problems related to a group may reappear, such as the tedious and time-consuming process of eliciting judgments, and additional sub-grouping could be necessary (7). If the MCDM methodology is to be used in group decision making, the analytic hierarchy process (AHP) (10) is probably one of the best choices. The AHP itself is a complete methodology for solving hierarchically structured decision problems. It elicits the decision maker’s (DM) judgment of elements in a hierarchy and mathematically manipulates them to obtain the final preference weights of the decision alternatives with respect to the overall goal. Although the method is originally developed to be used in individual decision making, extensions for group applications are achieved by establishing two typical aggregation contexts. The first is an aggregation of the individual judgments (AIJ) during the decision process, and the second is an aggregation of the individual priorities (AIP) of the evaluated alternative decisions once the decision process is completed. Finally, there are crisp and fuzzy versions of AHP with prevailing applications of the first. If the SCT based methodology is selected as being more favorable in group decision making, several approaches have been proposed for aggregating voters’ responses into a compromise ranking. Well-known election methods are plurality voting, the Hare system, the Borda count, pairwise comparisons voting and approval voting. All except the last are considered preferential methods based on ordinal preferences of candidates that are voted for. Voting methods serve as support in searches for collective choice, and many authors in the SC literature have suggested when and how to use them to find the best decision under conflicting preferences of the decision makers or interest groups. An interesting discussion and example application of SC methods in water resources management can be found in (7). In a group decision making context, MCDM and SC perform differently with respect to issues such as justice, fairness, or transparency to manipulation at various stages of implementation. Various authors report that the use of the two different MCDM (or SC) methods may easily declare different winners. As correctly noticed in (11) ‘… this is the main reason why comparison of different methods applied to the same problem is useful to both scientists and practitioners, since the detailed analysis of the results helps to find the most appropriate solution methodology in similar cases’. Voting systems (SCT methods)

Typically used SC methods are known as the preferential and non-preferential voting methods. All exclusively use ordinal preference information contained in the preference table created by collecting ballots (in real elections), by applying AHP (as is the case here), or by using a certain outranking method, etc. In this study we used three preferential and one non-preferential voting method. They are briefly presented below. The terminology from SC theory is slightly adjusted to make it comparable to the terminology used in the MCDM context. Preference schedule In applying voting methods, a special preference schedule table is useful to construct with the following properties. The size of the table is MxN, where M is the number of subgroups and N is the number of alternatives. Each row represents the ranking of the alternatives performed by one subgroup. If j is the best alternative for ith subgroup, then rank number is rij = 1; if j is the second best alternative, then rij = 2, and so on; if alternative j is the worst one, then rij = N. This way, each row of the preference table is simply a permutation of the integers 1,2,..., N. Plurality voting In this method, an alternative with the most first place ’votes’ wins. Notice, however, that the winner does not have to receive a majority of the first-place votes. Notice that the plurality voting uses only the ’first position’ information in the preference schedules that corresponds to the first place votes; all other

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information in the preference schedule is irrelevant. A major drawback of the method is that it is considered easy to manipulate. It has been shown that any non-dictatorial voting scheme is subject to manipulation, but some require more information to manipulate an election than others. Borda count In this method, each alternative gets 1 point for each first place vote received, 2 points for each second place, etc., all the way down to N points for each last place vote. The alternative with the lowest point total wins the election and is declared to be the social choice.

Pairwise comparisons voting In this method, each alternative is matched head-to-head with each of the other alternatives. Each alternative gets 1 point for a one-on-one win and a half a point for a tie. The alternative with the most total points is the winner. The method was explicitly designed to satisfy the fairness criterion called the ‘condorcet’, which addresses the fairness of declaring a candidate the winner even though some other candidate won all possible head-to-head matches. With the pairwise comparisons method, any candidate who wins all possible head-to-head matches always has a higher point total than any other candidate and thus is declared the winner. In group-subgroup decision making context, for each ordered pair (j1,j2) of alternatives, it is determined by how many subgroups alternative j1 is preferred to j2. If this number is denoted by N(j1,j2), alternative j1 is preferred to alternative j2 if N(j1,j2) > N(j2,j1), and alternative j1 gets a point. If N(j1,j2) = N(j2,j1), which may happen only if the number of sub groups is even, both alternatives j1 and j2 receive a half a point. The simple addition of points for each alternative match up declares the winning alternative, which is considered the social (group) choice. Notice that this voting method uses all the information from the preference schedule, but not all at once; while one pair of alternatives is matched up, the information about the other alternatives is ignored. In this regard, the Pairwise comparisons voting is similar to the Hare system, with the objection that in the later only the first place votes are used in each round. Notice also that in the presented voting methods so far, only the Borda count uses all the information in the preference table simultaneously. Approval voting The two presented voting methods are preferential because they use information directly from a preference schedule. Approval voting does not do so and is therefore considered as non-preferential. In this method, voters can vote for as many candidates as they wish. Each approved candidate receives one vote and the candidate with the most votes wins. Unlike more complicated ranking systems, approval voting is considered simple for voters to understand and use. In general, it has several compelling advantages over other voting procedures such as giving the voters more flexible options, helping to elect the strongest candidate, reducing negative campaigning, giving minority candidates their proper due. The method is also very practical, because adding or removing candidates does not change the point totals of the other candidates. If candidates drop out, it is enough to simply remove them from the list; if candidates are added, the vote totals for the original candidates remain the same, and voters only have to give their approval or disapproval of the candidates that are added. The approval voting is adapted for the group-subgroup decision making context used here. Let’s assume that consensus at a group level exists such that a certain number of top ranking alternatives will be approved from each subgroup list obtained by the use of AHP. Modified approval voting will then select the alternative that has the largest number of so approved votes.

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The AHP The AHP (analytic hierarchy process) method is developed by Saaty (10) as a complete methodology for solving hierarchically-structured decision problems. It elicits the decision maker’s (DM) judgment of elements in a hierarchy and mathematically manipulates them to obtain the final preference weights of the decision alternatives with respect to the overall goal. In the most general case, the criteria are first judged with respect to the overall goal then used as ’local goals’ for eliciting the DM’s judgment of the alternatives. The AHP is widely used for supporting individual and group decision making. Worthy of mention are some more recent investigations concerned with integrating the independent stages of group synthesis and prioritization in AHP into the unique process by methods such as goal programming, or fuzzy preference programming. Decision making within WUA (Illustrative example) Srdjevic and Srdjevic (12) suggested that the WUA’s assembly should work in plenary, while multi-criteria analysis and decision making should be conducted in a decentralized manner, in parallel IGs sessions. By assumption, any IG can autonomously select a decision making tool, e.g. AHP or any other well known tool such as PROMETHEE, TOPSIS, and ELECTRE; alternatively, IG can simply use brainstorming or internal communication as a means of simulation of the consensus-based decision making. In this illustrative example, each IG uses the AHP to evaluate the same set of five offered alternative annual action plans, provides a list of relative weights of plans, and all eight lists are forwarded to the assembly (decision making body) where the list are collected into a preference table to be used and come up to the final decision – to select most deirable annual plan for the WUA.. WUA Assembly as the decision making body The WUA Assembly is considered decision making body, composed of 28 members. Members are delegates of eight identified interest groups/stakeholders as given in Table 1. Majority of delegates (20) come from two relatively small neighbor watersheds in Vojvodina Province in Serbia. Three delegates represent the Public Water Management Company Vode Vojvodine responsible for overall water management in the Province. Inspection, responsible for control of contractual obligations and responsibilities of water users defined by law, is represented by three delegates from all three levels (state, province, local). Remaining four delegates are independent experts (2) coming from academy and representatives (2) of two non-governmental organizations.

Table 1. Composition of the decision making body (WUA Assembly)

Interest groups Number of delegates

IG1 Small irrigators 5 IG2 Large irrigators 6 IG3 PWMC Vode Vojvodine 3 IG4 Regional Water Company 4 IG5 Food industry 3 IG6 Inspection (state, province, local) 3 IG7 Independent experts 2 IG8 NGOs 2 Total 28

Decision alternatives and evaluation criteria

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The annual action plans prepared by WUAs administration and director are considered as decision alternatives and labeled as A1-A5. The Assembly has to decide which one of five offered alternative annual action plans should be implemented for next fiscal year. Before economic evaluation of plans’ implications should take place, the Assembly is willing to assess overall quality of action plans which is understood as the degree to which plans can meet water users’ needs to achieve their specific goals such as effectiveness, efficiency, satisfaction, freedom from risk, and overall satisfaction in various contexts of water use under auspices of the WUA. General definition of plans’ quality attributes are as follows: (1) Effectiveness relates to accuracy and completeness with which water users will achieve their

goals. A plan should poses functional suitability defined as degree to which it will provide functions that meet stated and implied needs under specified conditions

(2) Efficiency relates to monetary and material resources expended in relation to the accuracy and completeness with which water users will achieve goals. One of important aspects is will a plan demonstrate performance efficiency, that is a good performance relative to the amount of resources used under stated conditions

(3) Satisfaction relates to degree to which user needs are satisfied when a plan is implemented. (4) Freedom from risk relates to degree to which a plan mitigates the potential risk to water users’

economic status, human lives, health, and the environment. In particular it relates to degree to which a plan will achieve specified functions under specified conditions for a specified period of time. Close related to this is a reliability of a plan as degree to which a plan fulfils specified functions under specified conditions for a specified period of time. In addition, recoverability (resiliency) of plan with respect to a fault tolerance as degree to which a plan will be operations as intended despite the presence of negative impacts, faults and failures of equipment (e.g. irrigation facilities).

(5) Context coverage relates to degree to which a plan can be implemented in its specified context (water users’ association context) and in contexts beyond those initially explicitly identified (e.g., local, regional and broader economic context).

Results in AHP context The AHP computations created a data set presented in Table 2. Values represent relative importance associated to alternative plans by all IGs and their ranking. Various aggregation schemes are applicable to identify the most desirable plan for all participating IGs. Assuming equal importance of all IGs, geometrical aggregation produced the final weights of analyzed plans. The most desired is plan A1, followed by plan A2 , etc.

Table 2. Preference of alternatives by interest groups (AHP context)

Interest groups Alternatives A1 A2 A3 A4 A5

IG1 Small irrigators 0.23 (2) 0.38 (1) 0.10 (4) 0.22 (3) 0.07 (5) IG2 Large irrigators 0.13 (5) 0.21 (2) 0.17 (3) 0.35 (1) 0.14 (4) IG3 PWMC Vode Vojvodine 0.24 (2) 0.19 (3) 0.11 (5) 0.16 (4) 0.30 (1) IG4 Regional Water Company 0.09 (5) 0.24 (2) 0.45 (1) 0.08 (4) 0.14 (3) IG5 Food industry 0.35 (1) 0.27 (2) 0.10 (5) 0.11 (4) 0.17 (3) IG6 Inspection (state, province, local) 0.16 (4) 0.12 (5) 0.26 (1) 0.25 (2) 0.21 (3) IG7 Independent experts 0.27 (2) 0.17 (3) 0.08 (5) 0.16 (4) 0.32 (1) IG8 NGOs 0.37 (1) 0.16 (3) 0.07 (5) 0.15 (4) 0.25 (2) Aggregated 0.21 (1) 0.20 (2) 0.14 (5) 0.17 (4) 0.18 (3)

Results in SCT context

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The results obtained by AHP (see Table 1) are used within the three preferential and one non-preferential voting scheme to objectively rank the annual plans. Firstly, the preference schedule has been created as Table 3 and voting schemes produced the following rankings.

Table 3. Preference schedule of alternatives (SC context)

Interest groups Alternatives A1 A2 A3 A4 A5

IG1 Small irrigators 2 1 4 3 5 IG2 Large irrigators 5 2 3 1 4 IG3 PWMC Vode Vojvodine 2 3 5 4 1 IG4 Regional Water Company 5 2 1 4 3 IG5 Food industry 1 2 5 4 3 IG6 Inspection (state, province, local) 4 5 1 2 3 IG7 Independent experts 2 3 5 4 1 IG8 NGOs 1 3 5 4 2

Plurality voting: For each alternative, only the first places are considered as ‘voted’ by IGs. From table 2 it is easily seen that there is a tie of three alternatives (P1,P3, and P5). The complete ordering of alternatives is: A1 = A3 = A5 A2 = A4. The Borda count: From Table 4 it is obvious that winning alternative is A2 and that the complete ranking is: A2 A1 = A5 A4 A3.

Table 4. Borda Count ranking of Alternatives

Interest groups Alternatives A1 A2 A3 A4 A5

IG1 Small irrigators 2 1 4 3 5 IG2 Large irrigators 5 2 3 1 4 IG3 PWMC Vode Vojvodine 2 3 5 4 1 IG4 Regional Water Company 5 2 1 4 3 IG5 Food industry 1 2 5 4 3 IG6 Inspection (state, province, local) 4 5 1 2 3 IG7 Independent experts 2 3 5 4 1 IG8 NGOs 1 3 5 4 2 Sum of ranks 22 21 29 26 22 Ranking (2-3) (1) (5) (4) (2-3)

Pairwise comparisons voting: To identify the winner, alternatives are compared head-to-head. By scoring these match-ups (1 pt. for a win, 0.5 pts. for a tie), Table 5 is obtained.

Table 5. Points received in head-to-head comparisons

j1/j2 A1 A2 A3 A4 A5 A1 - 1 1 1 0 A2 0 - 1 1 0.5 A3 0 0 - 0 0.5 A4 0 0 1 - 0 A5 1 0.5 0.5 1 -

A direct match-up gives the following total of points: Alternative A1 – 3.0, Alternative A2 – 2.5, Alternative A3 – 0.5, Alternative A4 – 1.0, and Alternative A5 – 3.0. Notice that among the five

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alternatives, A1 and A5 are preferred overall by the three other alternatives; consequently, they are both considered as the DMG choice. The final ranking is: A1 = A5 A2 A4 A3. Approval voting: To apply this method, first the number of approved alternatives has to be specified. For this number being 2, only alternatives ranked as the first and as the second receive one vote and the others receive zero votes. Table 3 transforms into Table 6.

Table 6. Preference schedule of alternatives (SC context)

Interest groups Alternatives A1 A2 A3 A4 A5

IG1 Small irrigators 1 1 0 0 0 IG2 Large irrigators 0 1 0 1 0 IG3 PWMC Vode Vojvodine 1 0 0 0 1 IG4 Regional Water Company 0 1 1 0 0 IG5 Food industry 1 1 0 0 0 IG6 Inspection (state, province, local) 0 0 1 1 0 IG7 Independent experts 1 0 0 0 1 IG8 NGOs 1 0 0 0 1

The addition of votes by columns of Table 6 gives: V1=5, V2=4, V3=2, V4=2, V5=3. Since V1 is the largest, the alternative A1 is the DMG choice and the complete ordering by this method is: A1 A2 A5 A3 = A4. Discussion The results obtained by the AHP and four voting systems are summarized in Table 7. The first three ranked annual action plans in all cases are A1, A2 and A5. Taking into account structure of the methods used best choice is to combine AHP with Approval voting because they give the same ranking of the top three plans, namely: A1 A2 A5. A good balance is achieved if these two methods are combined because Approval voting is non-preferencial method which implies better acceptance in the Assembly of WUA after thorough application of preferential scheme contained in AHP.

Table 7. Preference schedule of alternatives (SC context)

Context Method Alternatives

MCDM AHP A1 A2 A5 A3 A4

SCT

Plurality voting A1 = A3 = A5 A2 = A4 Borda count A2 A1 = A5 A4 A3 Pairwise comparisons voting A1 = A5 A2 A4 A3 Approval voting A1 A2 A5 A3 = A4

By employing the methodology based on AHP only (the MCDM context), it is possible to control and preserve the consistency of the decision making process, but in fact the process excludes members of the decision making body such as the Assembly of the Water Users Association, or representatives of its constituent IGs, from the real decision making in the final stage of the process. On the other side, if a combination of MCDM and SC is implemented (the MCDM+SC context), during the SC phase (voting) important cardinal preference information obtained by AHP is not used, and only permutations of integer numbers are manipulated. Reduced information may lead to different outcomes for different voting methods, ties of alternatives etc. This exactly happened in presented example case study application. The compensation for this drawback is that there is a good chance (as shown here) that the goal will be achieved, and at least the best alternative will be recognized and posted to the first position in a list, especially if Aprroval voting system is used at the latest stage of a decisision making process. Worthy to mention is that voting may not necessarily be virtual (as simulated in this case

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example); it can be really performed thus giving a chance to IGs and their representatives to expose their choices in a more explicit and democratic way. Conclusions WUA, as an organizational form, in many countries represents a trustful concept that is well merged into the legal societal framework. There is no unique WUA model neither in terminology or the legislation behind it, but the base principles are the same. In most cases, the WUA is democratically controlled, established by its members, and has a similar internal structure. Most often, the WUAs are non-profit entities. Regarding legislation, selected rights are delegated to the WUA members that enable the WUA and demonstrate that it is capable to promote democracy and transparency, and to assure the fulfillment of the individual member’s rights. Rules are most commonly established in such a way that equity between ordinary and each member of the association is promoted in a positive way. An economic system transformation (socialism to capitalism) and related privatization processes in Serbia and Macedonia are underway, which means that the ownership structure is permanently changed in many instances. State owned properties are sold by tenders to private individual owners or their interest associations. Large agricultural areas have been already privatized, while water bodies (rivers, canals, and lakes with related infrastructure that includes lockers, pumping facilities, etc.) are public property and controlled by the state. There are thousands of small- and medium-sized farms (5-30 ha) along rivers and canals, and all this is important background for better understanding the importance of existing or planned WUAs in both countries. Our belief is that the AHP+SC approach has potential and flexibility. Better chances for adaptation in real life decision making we see in cases when decision making bodies anticipate the importance of decentralization and occasionally split into subgroups to preserve the homogeneity and overall consistency of the decision process, as well as assuring that the fundamental axioms of fairness and thrust will not be violated. References (1) D. Stacey, Water users organizations, Agricultural Water Management 40, 83-87 (1999). (2) O. Čukaliev, I. Iljovski, M. Vukelić-Šutoska, V.Tanaskovic, Hystory of Irrigation in Republic of Macedonia, In Proceedings of the 11-th Congress of the Serbian and Montentegro Society for Soil Science, Soil as a resource of sustainable development, Budva 2005, 50-57 (2005). (3) B. Srdjevic and Z. Srdjevic, Forming the water users associations in Vojvodina, Technical report for the Public Water Management Co. Vode Vojvodine, Novi Sad, Serbia (2009). (4) M. Gorton, J. Sauer, M. Peshevski, D. Bosev, D. Shekerinov and S. Quarrie, Water Communities in the Republic of Macedonia: An Empirical Analysis of Membership Satisfaction and Payment Behavior, World Development 37 (12), 1951–1963 (2009). (5) L.F. Cranor, Declared-strategy voting: an instrument for group decision making, Washington University, Ph.dissertation (1996). (6) E. Lakeman, How Democracies Vote: A Study of Electoral Systems, 4th Edition, Faber & Faber, London (1974). (7) B. Srdjevic, Linking analytic hierarchy process and social choice methods to support group decision making in water management, Decision Support Systems 42, 2261-2273 (2007). (8) N. Bolloju, Aggregation of analytic hierarchy process models based on similarities in decision makers’ preferences, European Journal of Operational Research 128, 499–508 (2001).

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(9) S. Zahir, Clusters in a group: Decision making in the vector space formulation of the analytic hierarchy process, European Journal of Operational Research 112, 620-634 (1999). (10) T.L. Saaty, The Analytic Hierarchy Process, McGraw-Hill, New York (1980). (11) A. d’Angelo, A. Eskandari and F. Szidarovszky, Social choice procedures in water resources management, Journal of Environmental Management 52, 203–210 (1998). (12) B. Srdjevic and Z. Srdjevic, Challenges of forming water users associations in Serbia, In Proceedings of the 16th Anual International Sustainable Development Research Conference 2010, Hong Kong, PRC (2010).