The present monograph is a synthesis of what has been contributed during the last decade to the analysis of market demand in large econ omies where consumers may have non-convex preference relations. Al though research in this field has not yet come to an end there exists a variety of interesting results, established in different frameworks by means of different conceptual and formal tools. a It is my aim to give comprehensive treatment of the existing lit erature including my own contributions. In working out differences and interrelations of the various ap proaches I adopted and modified several of the original results. My desire to present the problem and the methods by which it has been treated in such a way, that also non-specialists can follow, con flicted sometimes with the inevitable complexity of tools to be used. Therefore, I decided to give enough room to the introductory and prepa ratory part of this work. This part consists of the introduction and of the first four chapters. The main part of the present analysis consists of chapters 5 to 7.weiterlesen