A comprehensive approach for the selection of a portfolio of interdependent projects. An application to subsidized projects in Spain

Interdependency is an ubiquitous concept in project portfolio selection, both at the firm and industry levels. However, despite the wide acceptance of this fact, there is a remarkable scarcity of models involving interdependencies amongst non-financial investments. This paper presents a flexible model developed to address the scarcity of interdependency models: a fuzzy interactive multi-objective model, based on the reference point approach, which elicits the evaluation of interdependencies from a group of experts in a natural way. The model is presented in a sequential way, to highlight its contributions. Then, it is applied to solve a real portfolio selection problem, consisting on a large set of investment projects eligible for a subsidy program. The portfolio selected using the model achieves a sharp reduction in the deviations from objectives compared to the portfolio originally selected by the granting authorities.