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Why Do Individual Investors Hold Under-Diversified Portfolios?

Author

Listed:
  • WILLIAM N. GOETZMANN

    (Yale School of Management - International Center for Finance)

  • ALOK KUMAR

    (University of Notre Dame - Department of Finance)

Abstract

This study examines the diversification decisions of more than 60,000 individual investors during a six year period (1991-96) in recent U.S. capital market history. The majority of investors in our sample are under-diversified and the extent of under-diversification is more severe in retirement accounts. Investors' personal characteristics, their stock preferences, and their behavioral biases jointly influence their diversification choices. Younger, lower-income (less wealthy), and relatively less sophisticated investors and those who follow price trends, prefer local (familiar) stocks, and exhibit over-confidence hold relatively less diversified portfolios. Under-diversified investors exhibit strong style and industry preferences and they also prefer more volatile and positively skewed stocks. Furthermore, we find some evidence to support the asymmetric information hypothesis for under diversification. In contrast, we find that factors such as small portfolio size, transaction costs, and search costs are unlikely determinants of investors' diversification choices. The unexpectedly high idiosyncratic risk in investors' portfolios results in a welfare loss.

Suggested Citation

  • William N. Goetzmann & Alok Kumar, 2005. "Why Do Individual Investors Hold Under-Diversified Portfolios?," Yale School of Management Working Papers ysm454, Yale School of Management.
  • Handle: RePEc:ysm:somwrk:ysm454
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    Cited by:

    1. Ødegaard, Bernt Arne, 2009. "The diversification cost of large, concentrated equity stakes. How big is it? Is it justified?," Finance Research Letters, Elsevier, vol. 6(2), pages 56-72, June.
    2. James Choi & David Laibson & Brigitte Madrian, 2008. "The Flypaper Effect in Individual Investor Asset Allocation," Yale School of Management Working Papers amz2560, Yale School of Management.
    3. Kumar, Alok, 2007. "Do the diversification choices of individual investors influence stock returns?," Journal of Financial Markets, Elsevier, vol. 10(4), pages 362-390, November.
    4. H. Henry Cao & Bing Han & David Hirshleifer & Harold H. Zhang, 2011. "Fear of the Unknown: Familiarity and Economic Decisions," Review of Finance, European Finance Association, vol. 15(1), pages 173-206.
    5. Chang, Charles & Fuh, Cheng-Der & Hsu, Ya-Hui, 2008. "ESO compensation: The roles of default risk, employee sentiment, and insider information," Journal of Corporate Finance, Elsevier, vol. 14(5), pages 630-641, December.
    6. Chavas, Jean-Paul & Barham, Bradford L., 2007. "On the Microeconomics of Diversification under Uncertainty and Learning," Staff Papers 92141, University of Wisconsin-Madison, Department of Agricultural and Applied Economics.
    7. Jean-Philippe Bouchaud & Damien Challet, 2016. "Why have asset price properties changed so little in 200 years," Papers 1605.00634, arXiv.org.
    8. Nicholas Barberis & Ming Huang, 2008. "Stocks as Lotteries: The Implications of Probability Weighting for Security Prices," American Economic Review, American Economic Association, vol. 98(5), pages 2066-2100, December.
    9. Laurent E. Calvet & John Y. Campbell & Paolo Sodini, 2007. "Down or Out: Assessing the Welfare Costs of Household Investment Mistakes," Journal of Political Economy, University of Chicago Press, vol. 115(5), pages 707-747, October.
    10. Matus Medo & Chi Ho Yeung & Yi-Cheng Zhang, 2008. "How to quantify the influence of correlations on investment diversification," Papers 0805.3397, arXiv.org, revised Feb 2009.
    11. James J. Choi & David Laibson & Brigitte C. Madrian, 2009. "Mental Accounting in Portfolio Choice: Evidence from a Flypaper Effect," American Economic Review, American Economic Association, vol. 99(5), pages 2085-2095, December.
    12. Anderson, Anders, 2005. "Is Online Trading Gambling with Peanuts?," Sonderforschungsbereich 504 Publications 06-02, Sonderforschungsbereich 504, Universität Mannheim;Sonderforschungsbereich 504, University of Mannheim.
    13. Sengupta, Atri & Deb, Soumya Guha & Mittal, Shashank, 2021. "The underlying motivational process behind portfolio diversification choice decisions of individual investors: An experimental design," Journal of Behavioral and Experimental Finance, Elsevier, vol. 29(C).
    14. Lin, Yu En & Chu, Chien Chi & Omura, Akihiro & Li, Bin & Roca, Eduardo, 2020. "Arbitrage risk and the cross-section of stock returns: Evidence from China," Emerging Markets Review, Elsevier, vol. 43(C).
    15. Heena Thanki Joshi & Meghna Dangi, 2024. "Are Retail Investors in Emerging Economies SRI Ready?," Management and Labour Studies, XLRI Jamshedpur, School of Business Management & Human Resources, vol. 49(2), pages 256-274, May.
    16. Cheng, Teng Yuan & Lee, Chun I. & Lin, Chao Hsien, 2020. "The effect of risk-taking behavior on profitability: Evidence from futures market," Economic Modelling, Elsevier, vol. 86(C), pages 19-38.
    17. Ajamu Loving & Michael Finke & John Salter, 2012. "Explaining the 2004 Decrease in Minority Stock Ownership," The Review of Black Political Economy, Springer;National Economic Association, vol. 39(4), pages 403-425, December.
    18. Chae, Joon & Yang, Cheol-Won, 2013. "Commonality in individuals' trading: A systematic path between behavioral bias and expected returns," Pacific-Basin Finance Journal, Elsevier, vol. 21(1), pages 1008-1023.

    More about this item

    JEL classification:

    • G11 - Financial Economics - - General Financial Markets - - - Portfolio Choice; Investment Decisions
    • G12 - Financial Economics - - General Financial Markets - - - Asset Pricing; Trading Volume; Bond Interest Rates

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