supportive guidance throughout my thesis was always present and relevant. His trust, availability, and kindness were such that today I consider him as a friend. I would also like to thank the members of my thesis committee, Prof. Bernard Gendron, Dr. Daniel Costa, and Prof. Bernard Morard, for their constructive questions and remarks on this thesis. Thanks to all the members of the Geneva School of Economics and Management, the assistants, and especially my colleague Simon Thevenin. I wish you all good luck for your forthcoming careers.