Multi-criteria decision-making (MCDM) is one of the main decision-making problems used to determine the best alternative option, doing so by considering more than one criterion in the selection process [
1]. In cases where the choice of best alternative is highly complex, multi-criteria decision-making methods provide the possibility of determining the structure and solution by involving multiple criteria [
2]. The use of multi-criteria decision-making methods has increased significantly in different applications [
3]. One problem with MCDM methods is their uniqueness, which results the development of a vast number of theories, which while solving one specific problem always leaves unanswered questions [
4]. This statement, if it is true, implies that there is no best solution and that MCDM methods, even though they are very useful, still suffer from imperfections. To draw further conclusions, it is possible to state that every solution obtained via MCDM methods must be analyzed in detail to check their validity or to avoid drawing inaccurate conclusions. Another approach is to use the same method proposed for separating multiattribute utility theory (MAUT) models into two groups: riskless and risky choices [
5]. The other specific approach is to utilize multiattribute value theory (MAVT) models, which are a family of multi-criteria decision analysis methods that include stakeholders’ values in decision-making [
6]. Multiattribute decision-making (MADM) is cognitive process for evaluating data under various attributes to find the best option in terms of the preferences of the decision maker [
7]. The above-mentioned methods MAUT, MAVT and MADM are considered to be specific cases of general MCDM approaches, but of their differences have not been explained in detail.
Bearing in mind that decision-making is a complex mental process that is considered to result in the most desirable option considering different aspects, Taherdoost and Madanchian, 2023 [
1] imply that further research should be conducted to investigate certain situations in which a decision should be made. Analyzing the afore-mentioned statement, it is noticeable that two terms are important, namely “decision making is complex mental process” and “most desirable option”. Those two terms are quite indefinite and could be significantly dependent on the subjective preferences of the decision maker. This statement is valid even though the decision maker fulfilled the requirement defined by Nowak, 2007 [
8] because the decision maker will never have all the relevant information or obtain information in a stepwise manner. Another problem in the decision-making process is related to the situation when a group of decision makers have different preferences about alternatives. In that case, it is possible to state that the majority’s preferences should be accepted [
10]. According to Tang and Lin, Arrow’s impossibility theorem is “one of the landmark results in social choice theory” [
11]. This theoretical approach is researched with regard to the incompleteness of social preference and, by introducing the concept of minimal comparability, makes it possible to generate the complete social preference [
12]. Furthermore, other conditions become consistent with the hypothesis that the set of individuals is infinite [
13]. Of course, in practice, it is impossible to provide an infinite number of decision makers, but including a higher number of stakeholders in the process of decision-making should lead to a more acceptable solution. The problem of impossibility is recognized as very important, and there are other impossibility theorems such as those of Sen and Muller–Satterthwaite and Tang and Lin, 2009 [
11]. Some approaches used for researching impossibility theorems include the absence of collective rationality [
14], the absence of the Pareto principle [
15], and the existence of many agents and invisible dictators [
16]. Arrow’s theorem of impossibility could be explained using Boolean algebra [
17]. To solve the problem of impossibility, different approaches were utilized such as the model of the greatest common decision maker [
18] and the concept of fuzzy preference for a set of alternatives [
19]. Based on afore-mentioned references, it is obvious that the dominant approach used in dealing with Arrow’s impossibility theorem is based on the mathematical approach. Strictly speaking, Arrow’s theorem is valid except under specific conditions, especially when the differences in the preferences of decision makers are not insurmountable. Even if the preferences are insurmountable, the dominant preferences should be accepted in the decision-making process. Solving the problem of impossibility in the decision-making process (decision-making) implies that the differences between decision makers must be surmounted by different actions, including minimizing them and increasing the number of decision makers. According to the presented results for the comprehensive decision-making approaches, it follows that conducting careful research and directing decision makers to involve make reasonable effort to obtain the best possible solution are necessary steps. The term ‘reasonable effort’ means that the number of decision makers and decision-making approaches (MCDM methods) should both be increased. This increase should occur at a scale that does not affect the efficiency of decision-making.
In this research, all the above-mentioned steps will be considered and discussed carefully, especially the results of the decision-making process. In our case, the result of the applied MCDM method is the ranking of land consolidation projects, which was the initial issue of interest.
Desire can be defined very easily. For example, local authorities may want to choose the group of cadastral municipalities in which their goals are maximized. This legitimate desire is general and could be questioned from different aspects: Which goals do we want to achieve? How can we prioritize goals? Is there a set of goals acceptable for all stakeholders? A further problem is that different goals could be achieved if they are not defined precisely in advance. For example, are the goals predominantly related to agricultural production maximization or sustainable agricultural production? This simple example shows that general desire could be ambiguous and, if not precisely clarified in advance, the decision maker could not state if the decision-making process led to the best solution. On the other hand, when the goals are not clearly defined, opposite statements could be made. This situation is of extreme importance when there are numerous stakeholders competing for resources and interested in results of a decision-making process that considers their own interests. In the case of sensitive decision-making, the category where land consolidation projects belong, the precise definition of goals and their acceptance by all participants is of crucial importance. In that case, the goals must be the defined at a level of generalization acceptable for all participants and not be burdened by details that exclude the realization of a land consolidation process. The proper choice of goals can influence further decision-making, and mistakes made in this stage will affect the remaining process.
The decision maker should be aware of the environment in which land consolidation is realized. The environment is predominantly related to limitations, including a limited budget, legal limitations, the topographic characteristics of the area, available land and its distribution and participants’ interests. In the process of limitation determination, it is possible that some factors could be underestimated or overestimated and, consequently, certain errors in model could be introduced.
Aspects or criteria values for determination also could produce results with errors or that deviate from their true values. For example, some costs in the land consolidation process could be hidden or overlooked, some important aspects could be neglected and others of less importance could be overestimated, some characteristics of cadastral municipalities could be determined with less or more uncertainty, etc. Furthermore, the preferences of decision makers could differ significantly in the criteria (aspects) evaluation process. This step could lead to the overestimation of some criteria that objectively are not important for achieving goals and underestimate other, really important ones. This fact underlines the subjectivity component of the decision-making process.
Choosing the best MCDM method is also not easy because of the vast number of existing methods and their specificity. It could be assumed that different MCDM methods will generate results with different ranks for alternatives and that different decision makers will prioritize the criteria in different ways. This assumption implies that the application of different ranking determination methods depends on the number of decision makers involved and the number of MCDM methods applied.
The analytical matrix based on the afore-mentioned assumption is determined based on the number of decision makers involved (one or multiple) and the number of MCDM methods applied (one or multiple). This approach results in four possibilities: one decision maker and one MCDM method are applied (which means that the subjective views of one decision maker and one MCDM method are applied); one decision maker utilizes multiple MCDM methods (actually checking the differences between MCDM methods); multiple decision makers use one MCDM method (which means that potentially different preferences regarding criteria result in different ranks); multiple decision makers utilize different MCDM methods (which could lead to different ranks but represents the diversity of decision makers’ approaches to an issue). The process could also be complicated if different decision makers use different MCDM methods, but in this research, it is assumed that every decision maker will use the same set of MCDM methods.
The final step in the proposed approach is to check the results for obtained ranks. Results checking is based on evaluating the influence of the criteria on each rank. In this research, the evaluation of the criteria’s influence on the rank is based on performing multidimensional linear regression on the obtained rank results.
Analyzing the decision-making process, we can state that it is dependent on the situation in which decision is made. If one decision maker is free to choose the criteria and to weight them according to their preferences, the decision-making process is relatively simple: the decision maker can vary the weights and decide whether to apply one or more MCDM methods. In a situation when there are multiple decision makers, there is a high probability that every one of them will weight the criteria differently.
Bearing in mind the importance of making the best possible decision (especially for budget distribution), the complexity of the decision-making process and its imperfections, we simulated the decision-making process for multiple decision makers and multiple MCDM methods. This approach has been adopted and implemented for the dataset related to land consolidation project ranking and based on real data for the municipality of Bela Crkva, Serbia.
Theoretical Background
The vast number of MCDM methods and their variations suggests that no perfect MCDM method exists, and an implicit consequence of this fact is that it is very difficult (if even possible) to state that one method is superior to others. In further discussion, the authors try to elaborate the main characteristics of the utilized methods. In fact, the MCDM methods could be considered hybrid methods because the decision maker chooses the criteria, algorithm (method) and weights, while only the data are fixed [
21]. The hybridity of model is valid before these choices have been made—when those choices are made, it is possible to state that rank of alternatives is determined, even though the decision maker still does not know this before the rank is calculated. The only way to change the result is to change the initial choice. Consequently, for one dataset, the rankings of alternatives are always the same. This hybridity of one model (one model combines the subjective expert’s preferences regarding the alternatives and the choice of MCDM method, paired with objective data and an objective mathematical MCDM method) should not be confused with the hybrid approach resulting from the combination of MCDM methods. The first one should be considered to represent hybridity in the “narrow” sense, and other should be considered to represent hybridity in a “broader” sense.
The analytic hierarchy process (AHP) method among the most popular decision-making methods [
22]. The analytical hierarchy process was initially developed by Thomas L. Saaty and expanded into different domains of human activity by Hartwich, 1999 [
23]. The analytical hierarchy process is considered to be a means of applying exact methods in the decision-making process [
24]. This statement is valid, but this does not mean that the decision-making process will result in the best decision. It only means that the decision-making process, only as defined and for the adopted dataset, will result in identical ranks, regardless of the number of repeated calculations. The analytical hierarchy process is explained in detail in Saaty, 1980 and 2005 [
25,
26]. According to Saaty, everything one does consciously or unconsciously leads to some decision, and even though our judgment may be inconsistent, it is necessary to measure inconsistency and to improve the judgement [
27]. This is an important statement that underlines the imperfections of judgment as a complex and imperfect process, while highlighting that it is not an obstacle to improvement.
Although the AHP is popular and widely used in decision-making, research has presented critical opinions. In their book, Munier and Hontoria, 2021 [
28] analyzed the 30 subjects that highlight shortcomings and drawbacks in the AHP. Another criticism is that the AHP is very likely to provide a ranking of options that would not be acceptable to a rational person [
29]. Another problem with utilizing the AHP is that analysts may encounter a lack of data, deficient databases, defective information or, more importantly, a lack of specialists with adequate expertise [
30]. The sensitivity of consistency coefficient determined via the AHP is also an object of discussion: to be consistent, this measure should be less than 0.1, but the manipulation of objective weights indicates that if all objective weights are of near-equal importance, the consistency measure will require relatively consistent rankings of all objectives; otherwise, if one objective is much more important than the others, very little consistency is needed among the other objective ratings to pass the test limit [
31]. This paper underlines the sensitivity of the AHP method in terms of expressing the significance of the consistency coefficient near its value of delimitation, considering both consistent and inconsistent results. This issue could be termed as “consistency on a certain level” [
21]. This term refers to the situation when the decision maker does not care about rules proposed vis the AHP method for weighting alternatives and instead conducts the process intuitively or randomly accepts the values of weights.
Despite criticism, the AHP method is widely used for decision-making in different domains, often combined with SWAT (strength, weakness, opportunity, threat) analysis [
32], and it is considered the optimal choice for decision-making in forest management (despite its weaknesses) [
33]. Furthermore, the analytic hierarchy process should receive more attention than it has up to now and could be of great use in decision-making [
34]. In conclusion, we can state that, despite criticism, the AHP has a place both in theoretical research and practical application.
The Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is one of the most widely used multi-criteria decision-making methods, and it has various improved versions [
35]. The TOPSIS is numerical method, broadly applicable and simple in the mathematical sense [
36]. The TOPSIS is based on the idea that the best alternative is placed at the shortest distance from the positive ideal solution and the greatest distance from the negative one [
37]. The greatest distance from the most negative solution could be questionable, and another approach might be based on the distance from the veto threshold set by the decision makers [
38]. The influence of weights on the alternative ranking obtained via the TOPSIS showed that it is not noticeably more accurate than direct weighting methods; what is more, it is quite similar in accuracy except when equal weights are applied, leading to the conclusion that the most favorable aspect of the TOPSIS is that it determines accurate weights [
39]. Some noted imperfections of the TOPSIS resulted in its improvement. Starting from the basic idea of the TOPSIS, i.e., that it uses a pair of a positive and negative ideal solutions as two reference points to rank a set of alternatives and that, in some situations, those two distances may not be meaningful, one study proposed introducing a third middle reference point [
40]. A significant aspect of the development of the TOPSIS is its use of fuzzy logic [
41,
42,
43]; and many another studies). Regarding the utilization of the TOPSIS for ranking algorithms under evaluation (which the classical TOPSIS cannot do), the development of new algorithm was required [
44]. This case illustrates the adaptability and usability of the TOPSIS under contemporary conditions.
A literature review of a significant number of articles conducted over a decade showed that the TOPSIS continues to work satisfactorily across different application areas [
45]. This finding highlights that the TOPSIS is viable and reliable method for application in of decision-making process, even though it is still under development.
The MCDM method VIKOR (Serbian: Više Kriterijumska Optimizacija i Kompromisno Rešenje), meaning multi-criteria optimization and compromise solution, was developed in 1998 by Serafim Opricovic to solve decision problems with conflicting criteria and has attracted much attention for coping with complex problems with conflict factors [
46] (other authors state that the VIKOR method was proposed by Opricovic in 1979 [
47]). The VIKOR method is a widely used method, and, in 2009, the corresponding paper by Opricovic and Tzeng, 2004 [
47] became the most cited paper in the field of economics [
48]. The afore-mentioned authors questioned why this approach is empirically successful even though the model is very complicated and unintuitive, and they found one straightforward and one sophisticated justification by conducting detailed mathematical analyses [
48]. Another study conducted a systematic literature review of papers related to the VIKOR method published from 2004 to 2015 in high-ranking journals, most of which were related to operational research, management sciences, decision-making, sustainability and renewable energy, highlighting the usability of the VIKOR method in various theoretical and practical implementations [
49]. The VIKOR method can be used for material selection [
50], as well as for customer satisfaction-related thorough sentiment analysis schemes that simultaneously consider maximum group utility and individual regret [
51]. The spherical fuzzy VIKOR method is utilized for validating the complex spherical fuzzy model because of its adequacy for dealing with two-dimensional data [
52].
Depending on the specific decision problem, six variants of the VIKOR method have been subsequently developed, including comprehensive VIKOR, fuzzy VIKOR, regret theory-based VIKOR, modified VIKOR and interval VIKOR [
53]. All rankings obtained via different variants of VIKOR have produced different results, except the original and fuzzy VIKOR variants. Furthermore, VIKOR and other MCDM methods have been applied on an equal set of alternatives and criteria results with different rankings of alternatives. Utilizing PROMETHEE and VIKOR for choosing energy supply systems for space heating in residential buildings resulted in different sources of energy being used [
54]. One possible improvement in VIKOR is based on achieving distance improvement by implementing generalized weighted Mahalanobis distance, Euclidian distance and Canberra distance [
55]. Other improvements to VIKOR were made by including CRiteria Through Intercriteria Correlation (CRITIC) in the modified VIKOR technique to reduce the impact of expert preference [
56] and by integrating entropy and fuzzy VIKOR models [
57].
It is difficult to find research on the disadvantages of VIKOR in the literature. One of the disadvantages of VIKOR is that its subjective initial weighting is challenging to validate [
58], while other references stress improvements in this area [
59]. Among the advantages of fuzzy VIKOR (F-VIKOR) are simplicity, rational, comprehensibility and good computational efficiency, with the ability to measure the relative performances of alternatives in a simple mathematical form [
60]. The advantages of the original VIKOR method include handling both quantitative and qualitative data, providing a compromise solution that balances conflicting criteria and usability for problems with difficulties in expressing preferences, etc., while its disadvantages are related to sensitivity regarding changes in weights and thresholds, increased complexity with the number of criteria and alternatives, and requirement differences between initial weights, [
61]. The main disadvantage of VIKOR is its search compromise ranking order between expected and pessimistic solutions, which implies that changing weights can impact rankings (although this issue is considered a merit by some authors because it could identify the influence of weights on the alternatives’ rankings) [
62]. Summarizing the literature on VIKOR, most studies have been conducted with regard to its improvement and adaptation rather than stressing its disadvantages and shortcomings. Furthermore, the original VIKOR was not criticized when released, and its usability was not questioned seriously. These arguments recommend utilizing VIKOR method in this research.
Simple Additive Weighting (SAW) is known as weighted direct mix technique with a very simple mathematical model [
63]. SAW produces results very efficiently and easily, even when testing different cases [
64]. Comprehensive advantages and disadvantages of SAW encompass six cases in which efficiency is a major advantage and the following disadvantages: it may be applied when all variables are maximizing (but this requirement is solvable via normalization by converting minimizing variables into maximizing ones) and positive, and its results may not be logical [
65].
Summarizing the advantages and disadvantages of SAW, it is fair to include it in this research because of its simplicity and efficiency, as well as its widespread presence in contemporary research.
A further justification for authors utilizing multiple decision makers and MCDM methods in the process of choosing land consolidation projects is that a vast number of investigations are devoted to comparison rankings obtained via different MCDM methods applied on the same data, alternatives and criteria. Studying the utilization of the TOPSIS and VIKOR for ranking European countries based on aspects of the sustainable development goals (SDGs) has resulted in different rankings [
66]. Utilizing three MCDM methods, the TOPSIS, VIKOR and COPRAS (Complex Proportional Assessment), for COVID-19 showed that closest result to that of the Deep Knowledge Group consortium report was obtained using COPRAS and the most dissimilar result was obtained via VIKOR [
67]. Another interesting approach is utilizing a hybrid model (in this sense, “hybrid” denotes the utilization of two or more MCDM methods for making decisions). A review of 55 papers published from 1994 to 2019 indicated that a hybrid model combination of two or more MCDM methods is the most applied technique for material selection [
68]. Recently developed MCDM method combinations such as COPRAS and WASPAS (Weighted Aggregated Sum Product Assessment) are also utilized for material selection [
69]. A comprehensive literature review of papers published in 2008–2018 concluded that conducting further research on the creation of hybrid models could upgrade the existing MCDM methods [
70]. Another approach integrated FUCOM with the rough COPRAS method and utilized a rough Dombi aggregator, combining the positive aspects of the utilized MCDM methods to determine the stability of the best solution [
71]. The Hybrid MCDM (HMCDM) method, which combines multiple MCDM methods, could increase confidence in the obtained solution among single decision makers or groups of decision makers, especially in cases of increasing variety and complexity, as well as when facing more challenging problems [
72]. The main explanation for utilizing MCDM method combinations (hybrid MCDMs) is that different users (decision makers) will obtain different results by utilizing the same method since their backgrounds, expertise and experience differ [
73]. Even though every user (decision maker) of the MCDM method could have their own preferences, choice of alternatives and criteria evaluation approach, there still are some universal criteria for estimating the reliability of MCDM methods [
74]. The most important issue, i.e., whether different MCDM methods are benchmarkable, has been investigated and presented in the contemporary literature. Some research showed similarity with the final rankings obtained via different MCDM methods [
75], while other research showed that some applied MCDM methods (two) were determined to be more suitable methods than another five popular methods [
76].
Summarizing the literature that deals with the imperfections and/or limitations of utilizing one MCDM method and solving their imperfections/limitations with a hybrid approach, we can conclude that utilizing a hybrid approach has become imperative under contemporary conditions. Furthermore, every step in the decision-making process should be questioned seriously, and every MCDM method should be tested consciously to reduce the risk of possible mistakes.
These logical conclusions direct our research on ranking land consolidation projects. In this research, we adopt the following description of land consolidation (LC): LC represents a comprehensive reallocation procedure for a rural area consisting of fragmented agricultural or forest holdings or their parts, aiming to improve land division and to promote the appropriate use of the local real estate [
77]. Other points of view define LC as readjusting land parcels shapes, relocating land rights to minimize the farmland fragmentation, optimizing agricultural output, and generating optimal living and working conditions in rural areas [
78]. Land consolidation could provide multifunctional possibilities, including promoting rural revitalization, revitalizing the countryside, multi-objective and multifunctional transformation, and social, economic and ecological benefits, but its potential risks cannot be ignored [
79]. The latest justification for land consolidation seems to be the most comprehensive, because it encompasses the consequences of land consolidation projects, i.e., both benefits and potential risks. This approach is suitable for decision-making because it requires serious consideration, especially considering the budget needed for realizing land consolidation projects. It should be stressed that there were investigations that considered the application of different MCDM methods in land consolidation project prioritization. The suitability of cadastral municipality ranking based on information by applying three different multi-criteria methods is suitable for national agricultural or other spatial planning purposes [
80]. An integrated assessment methodology for land consolidation projects was proposed for the improving decision-making process [
81].
Without further developing the LC in detail, we can state that LC projects are quite complex, and the main limitation hindering their realization is a limited budget. In that case, it is necessary to determine which LC projects among all competitive options should be realized within the available budget. Considering the significance of realizing LC projects, it is of crucial importance to provide the most accurate ranking among competitive projects to determine the best budget distribution.
The research should answer a fundamental set of questions derived from the above-proposed decision-making process (
Figure 1):
- -
Are the criteria that describe land consolidation projects well chosen (is the goal well reflected in the criteria)?;
- -
How does the environment (limitation values of criteria and alternatives) affect the choice of land consolidation project?;
- -
Do the different approaches for weighting criteria affect the rank of land consolidation projects (is the environment understood well?)?;
- -
How does the applied method impact the rank of land consolidation projects?
- -
Are the results of different MCDM method-based land consolidation project rankings mutually consistent?
Due to the complexity of the questions formulated, it is not possible to cover and present all of them in this paper; thus, the authors focused only the question “does the application of multiple decision makers and multiple MCDM methods lead to a more consistent choice of land consolidation project?” Consistency in this context means that the choice will be more reflective of the real situation. The measure of consistency is obtained using the decrease in standard deviation between rankings of the same project and the difference between them. This question seems to be neglected in the analyzed literature. In this research, four methods were used: AHP, the TOPSIS, VIKOR and SAW; they were applied to land consolidation projects for the Bela Crkva (Republic of Serbia, Vojvodina) municipality.