First Author:   Flip Klijn Departamento de Estatística e Investigación Operativa, Universidade de Vigo, Spain fklijn@uvigo.es         Second Author: Stef Tijs Department of Econometrics and CentER, Tilburg University, The Netherlands s.h.tijs@kub.nl         Third Author: Marco Slikker Department of Technology Management, Technische Universiteit Eindhoven, The Netherlands m.slikker@tm.tue.nl