Keynes Meets Markowitz: The Trade-Off Between Familiarity and Diversification

Phelim Boyle (), Lorenzo Garlappi (), Raman Uppal and Tan Wang
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Phelim Boyle: School of Business and Economics, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
Lorenzo Garlappi: Sauder School of Business, University of British Columbia, Vancouver, British Columbia V6T 1Z2, Canada

Management Science, 2012, vol. 58, issue 2, 253-272

Abstract: We develop a model of portfolio choice to nest the views of Keynes, who advocates concentration in a few familiar assets, and Markowitz, who advocates diversification. We use the concepts of ambiguity and ambiguity aversion to formalize the idea of an investor's "familiarity" toward assets. The model shows that for any given level of expected returns, the optimal portfolio depends on two quantities: relative ambiguity across assets and the standard deviation of the expected return estimate for each asset. If both quantities are low, then the optimal portfolio consists of a mix of familiar and unfamiliar assets; moreover, an increase in correlation between assets causes an investor to increase concentration in familiar assets (flight to familiarity). Alternatively, if both quantities are high, then the optimal portfolio contains only the familiar asset(s), as Keynes would have advocated. In the extreme case in which both quantities are very high, no risky asset is held (nonparticipation). This paper was accepted by Brad Barber, Teck Ho, and Terrance Odean, special issue editors.

Keywords: investment; portfolio choice; ambiguity; robust control; underdiversification (search for similar items in EconPapers)
Date: 2012
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Citations: View citations in EconPapers (88)

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Working Paper: Keynes Meets Markowitz: The Trade-off Between Familiarity and Diversification (2010)
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Persistent link: https://EconPapers.repec.org/RePEc:inm:ormnsc:v:58:y:2012:i:2:p:253-272

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