## 2 Methods and Variables  
### Setting the Explanatory Framework  
Agricultural scholars have developed a range of theoretical schemes and methods to model the behavior of farmers when they have to make decisions regarding different kind of topics [23]. The types of factors affecting the decisions of farmers, already been used in the agricultural literature, vary according to the type of decision to be modeled by each study [16]. Nevertheless, some basic factor categories remain common among the various frameworks which are mostly related to the characteristics of the farmer and the agricultural holding, the situational factors that may affect the behavior of the farmer, farmers' personal beliefs and attitudes around some relevant issues with the topic of decision, and finally the perception of farmers regarding the different choices related to the decision problem at stake [15; 16; 24]. [PERSON] et al. [25], in their review paper on factors affecting farmers' participation in biodiversity policies, provide a good summary of the factors using a three-category explanation scheme. The first category, called \"farmers' willingness\", is shaped by all perceptions of farmers based on subjective judgments, such as beliefs, interests, values and awareness of the problem at stake. The second category is this of \"direct and wider social influences\" and refers to the factors that capture the effect of the social interactions and the influence of the social, political, and economic environment. Finally, the third category is \"farmers' ability\" and includes their demographic characteristics, the structural characteristics of their farm, and generally all the conditional factors influencing their decision-making process. On the methodological setting of studies on farmers' decision-making modeling, there could be distinguished two main categories of approaches. In the first category there exist methods that are based on actual observations of field research and surveys to econometrically estimate the effect of various factors on the decision behavior of farmers, while at the opposite side stand methods which are based on experiments, in order to model their decision-making process. The great advantage of econometric methods is that estimations are based on actual data and therefore are more connected to reality. On the other hand, econometric methods cannot be used for ex ante evaluations, a feature that is only feasible with the experimental approach [16; 26]. Therefore, it is on the researchers' judgment to select which path better suits their research targets, always considering the kind of data that are available for conducting the analysis. Considering the scarcity of studies on farmers' decision-making for participation in PRP, the present framework relies on factors that have been used by studies on ES and complement them with some additional factors emanating from the broader literature on farmers' decision-making [17]. These factors have succeeded to identify motivation leading to ES participation, based on relative decision theories [20]. In addition, it should be noted that the variables' selection is also driven by our experience gained through the preparation of two research proposals under a research call for collaborative schemes between universities and farm holdings representatives, co-financed by the European Union (EU) and the Greek State. During our research for receiving some initial expressions of interest from farmers, we came across a generally negative attitude of farmers, which was justified by different reasons. As the replies of farmers were not recorded in the context of a dedicated survey, we cannot document in a quantitative approach the frequencies of the reasons that farmers reported as impeding their participation. However, we can document that the majority of refusals were mainly justified on the lack of trust to universities and the EU, lack of motive, unclear benefits, lack of financial capacity, and a general lack of knowledge around the framework on which the PRPs are built.