HANDBOOK OF THE FUNDAMENTALS OF FINANCIAL DECISION MAKING Part I World Scientific Handbook in Financial Economic Series (ISSN: 2010-1732) Series Editor: William T. Ziemba University of British Columbia, Canada (Emeritus); ICMA Centre, University of Reading, UK; Visiting Professor at The Korean Advanced Institute for Science and Technology and Sabanci University, Istanbul Advisory Editors: Harry M. Markowitz Kenneth J. Arrow University of California, USA Stanford University, USA Robert C. Merton George C. Constantinides Harvard University, USA University of Chicago, USA Stewart C. Myers Espen Eckbo Massachusetts Institute of Technology, Dartmouth College, USA USA The Handbooks in Financial Economics (HIFE) are intended to be a definitive source for comprehensive and accessible information in the field of finance. Each individual volume in the series presents an accurate self-contained survey of a sub-field of finance, suitable for use by finance, economics and financial engineering professors and lecturers, professional researchers, investments, pension fund and insurance portfolio mangers, risk managers, graduate students and as a teaching supplement. The HIFE series will broadly cover various areas of finance in a multi-handbook series. The HIFE series has its own web page that include detailed information such as the introductory chapter to each volume, an abstract of each chapter and biographies of editors. The series will be promoted by the publisher at major academic meetings and through other sources. There will be links with research articles in major journals. The goal is to have a broad group of outstanding volumes in various areas of financial economics. The evidence is that acceptance of all the books is strengthened over time and by the presence of other strong volumes. Sales, citations, royalties and recognition tend to grow over time faster than the number of volumes published. Published Vol. 1 Stochastic Optimization Models in Finance (2006 Edition) edited by William T. Ziemba & Raymond G. Vickson Vol. 2 Efficiency of Racetrack Betting Markets (2008 Edition) edited by Donald B. Hausch, Victor S. Y. Lo & William T. Ziemba Vol. 3 The Kelly Capital Growth Investment Criterion: Theory and Practice edited by Leonard C. MacLean, Edward O. Thorp & William T. Ziemba Vol. 4 Handbook of the Fundamentals of Financial Decision Making (In 2 Parts) edited by Leonard C. MacLean & William T. Ziemba Forthcoming The World Scientific Handbook of Insurance (To be announced) The WSPC Handbook of Futures Markets edited by A. G. Malliaris & William T. Ziemba Alisha - Hdbk of the fundamentals of Finan.pmd1 2/18/2013, 10:39 AM World Scientific Handbook in Financial Economic Series — Vol. 4 HANDBOOK OF THE FUNDAMENTALS OF FINANCIAL DECISION MAKING Part I Editors Leonard C MacLean Dalhousie University, Canada (Emeritus) William T Ziemba University of British Columbia, Canada (Emeritus); ICMA Centre; University of Reading, UK; Visiting Professor at The Korean Advanced Institute for Science and Technology and Sabanci University, Istanbul World Scientific NEW JERSEY • LONDON • SINGAPORE • BEIJING • SHANGHAI • HONG KONG • TAIPEI • CHENNAI Published by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE Library of Congress Cataloging-in-Publication Data Handbook of the fundamentals of financial decision making (in 2 Parts) / edited by Leonard C. MacLean and William T. Ziemba. v. cm. -- (World scientific handbook in financial economic series, ISSN 2010-1732 ; v. 4) Includes bibliographical references and index. ISBN 978-9814417341 (Set) ISBN 978-9814417372 (Part I) ISBN 978-9814417389 (Part II) 1. Investments--Decision making. 2. Finance--Decision making. 3. Risk management. 4. Uncertainty I. MacLean, L. C. (Leonard C.) II. Ziemba, W. T. HG4515.H364 2013 332--dc23 2012037307 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Copyright © 2013 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. In-house Editor: Alisha Nguyen Typeset by Stallion Press Email: [email protected] Printed in Singapore. Alisha - Hdbk of the fundamentals of Finan.pmd2 2/18/2013, 10:39 AM March12,2013 15:8 HandbookoftheFundamentalsofFinancialDecisionMaking 9.75inx6.5in b1436-fm-vol-1 This part is dedicated to the memory of Professor Paul Anthony Samuelson, arguablythemostinfluentialeconomistofthe20th centuryandamajorcontributor to the topics in this handbook. Paul was born in Gary Indiana on May 15, 1915 and died in Belmont, MassachusettsonDecember 13,2009.He wasInstitute ProfessorofEconomicsand Gordon Y Billard Fellow at the Massachusetts Institute of Technology. v March12,2013 15:8 HandbookoftheFundamentalsofFinancialDecisionMaking 9.75inx6.5in b1436-fm-vol-1 TThhiiss ppaaggee iinntteennttiioonnaallllyy lleefftt bbllaannkk March12,2013 15:8 HandbookoftheFundamentalsofFinancialDecisionMaking 9.75inx6.5in b1436-fm-vol-1 Preface Thetheoryandpracticeofdecisionmakinginfinancehasalongandstoriedhistory. Many of the fundamental concepts in economics as wellas the models in stochastic optimization have their origins in finance. In this handbook, a selection of the key papersinfinancialdecisionmakingarebroughttogethertoprovideacomprehensive picture of the components and methods. The handbook is composed of two parts. Part I consists of a collection of reprints of seminal papers on the foundations of decision making in finance. Part II contains mostly original papers which explore aspects of decision models. A special emphasis is placed on models which optimize capital growth. In Section A of Part I, the concept of arbitrage is presented in a set of papers. Arbitrage is an opportunity for risk free gains, and an absence of arbitrage is a condition for a stable financial market. The seminal paper is from Ross (1976), where the Arbitrage Pricing Theory (APT) is introduced. He defines the prices on assets by a linear relation to common factors (latent random variables) each with expectation zero. After accounting for risk there is no price premium, that is, arbitragedoesnotexist.Anotherwayofstatingthisconditionisthatafteradjusting for risk, the price process is a martingale. TheFundamentalTheoremofAssetPricingstatesthat“noarbitrage”isequivalent totheexistenceofanequivalent“martingalemeasure.”ThepapersbySchachermayer (2010a,2010b)putthefundamentaltheoreminageneralsetting.Thereexistsamar- tingalemeasureifandonlyifthepriceprocesssatisfiesanofreelunchwithvanishing riskcondition.Themartingalemeasureisarisk-neutralmeasureandallassetshavethe sameexpectedvalue(therisk-freerate)undertherisk-neutralmeasure. Kallio and Ziemba (2007) use Tucker’s theorems of the alternative from math- ematical programming to establish the existence of risk neutral probabilities for the discrete time and discrete space price process. The equivalence between no arbitrage and the existence of a martingale measure is extended to markets with various imperfections. The concept of utility as an expression of preference is developed in Section B. Fishburn’s paper (1969) gives a succinct presentation of expected utility theory. With a set of assumptions over decision maker preferences, Fishburn establishes the existence of a utility function and subjective probability distribution such that rationalindividuals actas thoughthey weremaximizingexpected utility.Expected utility allows for the fact that many individuals are risk averse, meaning that the individual wouldrefuse a fair gamble(a fair gamblehas anexpected value of zero). vii March12,2013 15:8 HandbookoftheFundamentalsofFinancialDecisionMaking 9.75inx6.5in b1436-fm-vol-1 viii Preface In expected utility theory, the utilities of outcomes are weighted by their prob- abilities. Machina (2004) in his paper describes non expected utility. It has been shownthat people overweightoutcomes that are consideredcertain relativeto out- comes which are merely probable. There have been a variety of proposals for deal- ing with the violation of the independence axiom and the linearity in probabilities. One approach is Prospect Theory proposed by Kahneman and Tversky (1979). The value function is S-shaped, being convex for losses (x < 0) and concave for gains (x>0). ProspectTheoryhasitscritics.ThepapersbyLevyandLevy(2004)castdoubt on the S-shaped value function, based on experimental results. The basis of their analysis is stochastic dominance which orders random variables. The paper by Wakker (2003) reinforces the importance of probability weighting as well as the S-shaped value in prospect theory. He re-examines the experiments, showing that the S-shape is compatible with the data when probability weighting is used cor- rectly. Baltussen et al. (2006) provide experimental results supporting the usual risk averse (concave) function over either the S-shape or reverse S-shape. Infinancialdecisionmaking,the(investment,consumption)processisdynamic, with the alternatives consisting of investment and consumption decisions at points intime.KrepsandPorteus(1979)considertheinter-temporalconsistencyofutility for making dynamic decisions. Preferences at different times are linked by a tem- poral consistency axiom, so that decisions are consistent in the sense that revealed outcomes at a later time would not invalidate the optimality of earlier decisions. ThepaperbyEpsteinandZin(1989)buildsonthetemporalutilityformtodefine a recursive utility which incorporates inter-temporal substitution and risk aversion separately.The Epstein–Zinutility contains many popular utility functions suchas power utility as special cases. In Section C, the preference for random variables with the order relations of stochasticdominanceareconsidered.HanochandLevy(1969)showthatstochastic dominance can be defined by classes of utilities as characterized by higher order derivativesoftheutility,withu(k)beingthekthderivative.Thedominancedescribed is for a single period, usually the final period of accumulated capital. However,the capitalisaccumulatedfrominvestmentsovertimeandthetrajectorytofinalwealth could be important in the assessment of utility. Levy and Paroush (1974) extend the notions of stochastic dominance to the multi-period case. With additive utility the stochastic dominance result is extended to multiple periods. Levy and Paroush also consider the geometric process where the final return is the product of period returns and give necessary conditions for first order dominance. Efficient investment strategies, where risk is minimized for specified return, are the topic of Section D. A major advantage of Markowitz’mean-varianceanalysis is the relative ease of computing optimal strategies and as such it is a practical tech- nique. The paper by Ziemba, Parkan and Brooks-Hill (1974) considers the general risk-return investment problem for which they propose a 2-step approach: the first step is to find the proportions invested in risky assets using a fractional program; the second step is to determine the optimal ratios of risky to non-risky assets. March12,2013 15:8 HandbookoftheFundamentalsofFinancialDecisionMaking 9.75inx6.5in b1436-fm-vol-1 Preface ix Ziemba (1975) considers the computation of optimal portfolios when returns have a symmetric stable distribution. The normal is a stable distribution when the variance is finite, but the stable family is more general with dispersion replacing variance and has four rather than two parameters. The typical utility function in the investment models is concave to reflect risk aversion. There are aspects of risk aversion which are not captured by concavity. In the paper by Pratt (1964),an additional property of utility, decreasing absolute risk aversion,is introduced. Rubinstein (1973)develops a measure ofglobalrisk aversionin the context ofa parameter-preference equilibrium relationship. Some properties of this measure in the context of risk aversion with changing initial wealth levels appear in Kallberg and Ziemba (1983). Kallberg and Ziemba establish an important property of the globalrisk measure:Investors with the same risk have the same optimal portfolios. Chopra and Ziemba (1993) consider the relative impact of estimation errors at variousdegreesofriskaversiononportfolioperformance,withtheestimateofmean return being most important. MacLean, Foster and Ziemba (2007) use a Bayesian framework to include the covariance in an estimate of the mean. In essence, the return on one asset provides information about the return on related assets, and thesharingofinformationthroughthecovarianceimprovesthequalityofestimates. Expected utility may not be the right theory for many risk attitudes, and does not explain the modest-scale risk aversion observed in practice. Rabin and Thaler (2001)intheirpaperproposethattherightexplanationincorporatestheconceptsof lossaversionandmentalaccounting.Theyarguethatlossaversionandthetendency to isolate each risky choice must both be components of a theory of risk attitudes. Part II The basic components of risk are (i) the chance of a potential loss and (ii) the size of the potential loss. F¨ollmer and Knipsel (2012) view the financial risk of X as the capital requirement ρ(X) to make the position X acceptable, with the corre- sponding acceptance set of positions for measure ρ. With reference to acceptance sets, Rockafeller and Ziemba (2000) have established the following result: There is a one-to-one correspondence between acceptance sets Aρ and the risk measures ρ. Theconceptofcapitalrequirementtocoverthe lossesfrominvestmentcaptures thefinancialriskidea,buttheprobabilityoflossisnottakenintoaccount.Detailson measures which use the distribution are provided in the papers of Krokhmal et al. (2011) and Fo¨llmer and Knipsel (2012). Deviation measures are a generalization of variance. There is a one-to-one relationship between averse risk measures and deviation risk measures. A variationis to consider the averageof the values at risk (AVaR). F¨ollmer and Knipsel show how AVaR is a building block for law-invariant risk measures. Since convexity is the desired property of a risk measure, the class of convex risk measures is considered in F¨ollmer and Knispel (2012), following Rockafeller and Ziemba (2000). Fo¨llmer and Knispel also raise the issue of model uncertainty
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