The views expressed in this study are those of the author and do not necessarily reflect the views of the United Nations. The designations employed and the presentation of the material do not imply the expression of any opinion whatsoever on the part of the United Nations Secretariat concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. Material in this publication may be freely quoted or reprinted, but acknowledgement is requested, together with a reference to the document number. A copy of the publication containing the quotation or reprint should be sent to the UNCTAD secretariat: Chief Trade Analysis Branch Division on International Trade in Goods and Services, and Commodities United Nations Conference on Trade and Development Palais des Nations CH-1211 Geneva UNCTAD/ITCD/TAB/21 UNITED NATIONS PUBLICATION Sales No. E.02.II.D.10