# Critical Factors for Green Public Procurement: The Case of Greece
## 3 Methodology
During the second phase, the DEMATEL method was used in cooperation with experts (procurement executives in the Greek public sector) in order to exploit their experience and knowledge in this field. The initial selection comprised public sector employees who had participated in training activities in the field of GPP since 2021. They were subsequently assessed on the basis of their experience (\(\geq\) 5 years) in public procurement. An invitation to participate was initially sent to 19 executives, of which 16 decided to participate. Two of the participants were excluded as they did not actually have the required experience in public procurement, and eventually fourteen executives participated (thirteen females). Twelve held a bachelor's university degree and one held a Ph.D. degree. Their overall working experience, as well as their experience in the field of public procurement, are presented in Figure 3.  
A semi-structured interview was first conducted with each participant in order to analyze the context and purpose of the research and to resolve any questions. In addition, they were reassured regarding the protection of their personal data, confidentiality, and the protection of information coming from their organizations. Each one of them provided their consent to participate and was free to end the survey at any time if the questions or the format were deemed uncomfortable. The identified CFs were assessed through experts' responses to the questionnaires and were analyzed using the grey DEMATEL method. The questionnaire was structured in three sections. The first section sought the demographic information of the participants regarding the details of the government agency by which they were employed, their years of experience, and their educational level. In the second section, participants were asked to rank the CFs according to the degree of their importance. In the third section, the degree of influence of each factor on the others was captured according to the linguistic scale shown in Table 2 and as reflected in the experts' responses. Figure 3: Executives’ overall working experience and working experience specifically in public procurement. The DEMATEL method [27] was developed by the Battelle Memorial Institute of Geneva between 1972 and 1976 to address complex problems by identifying the crucial elements that must be considered and their causal connections. The advantage of this method in relation to other approaches is its ability to find the interdependencies among factors regarding their impact from the decision-makers' perspectives [28]. In recent years, DEMATEL has proven to be a popular multi-criteria decision-making tool to help address practical evaluation problems compared to other methods. For instance, a wider breakdown is possible with DEMATEL compared to Interpretive Structural Modeling (ISM). In DEMATEL, the intensity of the correlations between the components can vary widely in range, whereas in ISM the levels range from 0 to 1. While the Analytic Hierarchy Process (AHP) only permits unidirectional relationships and yields several independent matrices that require integration, in contrast, DEMATEL stands out as it permits the possibility of multiple directional relationships [29]. Moreover, the Analytic Network Process (ANP) is capable of handling criteria reliance and feedback but the assumption of equal weight for each cluster, which is required to obtain a weighted supermatrix in the ANP, is not reasonable in practical situations [30]. One disadvantage of DEMATEL is the difficulty of evaluating ambiguous scenarios when there is disagreement among experts, mainly due to a lack of tacit knowledge [31]. Nevertheless, it is very practical for situations with small sample sizes or uncertain data, and it is simple to integrate with other decision-making techniques to assess the accuracy of the inferences [32]. Grey theory is a mathematical theory proposed to cope with systems that lack information.