This book grew out of a 'Doctorat D'Etat' thesis presented at the University of Dijon-Institut Mathematique Economiques (lME). It aims to show that quantity rationing theory provides the means of improving macroeconometric modelling in the study of struc- tural changes. The empirical results presented in the last chapter (concerning Portuguese economy) and in the last Appendix (con- cerning the French economy), although preliminary, suggested that the effort is rewarding and should be continued. My debts are many. An important part of the research work was accomplished during my visit to the...