(en) The need for study of firm investment behaviour has now become more important in order to assess the effects of economic policies on the potential production and employment, because many changes in economic structures have occured since the beginning of the so-called economic crisis in Western countries. This period can be characterized by the end of fast growth, the entrance of Japan and new industrialized countries of The Far East in the international trade, the instability and the uncertainty affecting monetary and financial markets, the increasing disequilibrium of internal or external balances, the rise of mass unemployment in many countries and the appearance of new technologies concerning the production and the organization of firms.