In the wake of the publication of Forrester's World Dynamics and Meadow's The Limits to Growth-books which in The Netherlands may have received ex­ cessive attention from the public at large-the Netherlands Organization for Applied Scientific Research (TNO) established a commission under the chair­ manship of the late Professor R. Timman. The commission received the task of trying to find a sound philosophical basis for world modelling and to stimulate the building of models that incorporated those aspects of society which are usu­ ally left out of mathematical models because of technical difficulties. The study that is discussed in this text was started under the auspices of the TNO commis­ sion. Timman died early in 1975. The commission then came under the chair­ manship of Professor P. de Wolff. TNO generously provided the means to acquire the computer time necessary to continue our study. We also wish to express our gratitude to the Statistical Office of the European Communities (SOEC) for their willingness to put the necessary data at our dis­ posal in a form suitable for computer processing. Mr. H. Krijnse Locker's expert knowledge in the field of input-output statistics has especially been of great sup­ port to us. We are much indebted to Professor A. P. J. Abrahamse for his interest in our work and for all the valuable comments and corrections we received from him. v vi PREFACE We are grateful to Mr. P. van Batenburg, Mr. F.