A REVISED GEOMETRY OF MEAN-VARIANCE EFFICIENT PORTFOLIOS

A revised definition of efficiency compares portfolios with different net worths. One axiom rules out instantaneous riskless gains, the other asserts that it costs money to buy good portfolios. Unlimited short sales are allowed. Portfolios which cannot be improved at any price are called absolutely efficient. The geometry of the mean-standard deviation frontiers is governed by three “efficient set constants”. A few results regarding efficient portfolios must be modified, and a new version of the security line equation is proposed. Explicit formulas are given: no need to use different formulas for singular or non-singular covariance matrix.     

BOOK REVIEWS

Dynamics and Conflict in Regional Structura1 Change—Essay in Honor of Walter Isard Volume 2 Practical Methods of Regional Science and Empirical Applications—Selected Papers of Walter Isard, Volume 2 Department of Economics Loughborough University Export Promotion Strategies—Theory and Evidence from Developing Countries Commonwealth Secretariat Export Market Development Division Human Development Report 1990 for the United Nations Development Programme (UNDP) (New York and Oxford: University of Nottingham The World Bank and the Environment—First Annual Report Fiscal 1990, The World Bank (New York: The World Bank, 1990 London Environmental Economics Centre University College London The European Communities' Single Market: The Challenge of 1992 for Sub-Saharan Africa Loughborough University     

Einzelbesprechungen

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De binnenlandsche geldmarkt en de Nederlandsche Bank in 1907

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