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Portfolio Concentration and the Performance of Individual Investors

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  • Zoran Ivkovich
  • Clemens Sialm
  • Scott Weisbenner

Abstract

Using data on the investments a large number of individual investors made through a discount broker from 1991 to 1996, we find that the stock trades by households with concentrated portfolios outperform those with diversified portfolios. While in general the stocks bought by individual investors significantly underperform the stocks they sell, the reverse is true for households whose holdings are concentrated in a few stocks. The excess return of concentrated relative to diversified portfolios is stronger for households with large account balances as well as for stocks not included in the S&P 500 Index and local stocks, potentially reflecting concentrated investors' successful exploitation of information asymmetries. This finding is very robust to alternative concentration measures and regression specifications, and to alternative explanations such as differences across concentrated and diversified investors in the portfolio turnover and access to inside information, suggesting that some of these concentrated households have superior information processing skills. Moreover, controlling for a household's average investment ability, the household's trades perform better as the household's portfolio includes fewer stocks. However, while concentrated household portfolios on average outperform diversified ones, their levels of total risk are larger and the Sharpe ratios of their stock portfolios are lower.

Suggested Citation

  • Zoran Ivkovich & Clemens Sialm & Scott Weisbenner, 2004. "Portfolio Concentration and the Performance of Individual Investors," NBER Working Papers 10675, National Bureau of Economic Research, Inc.
  • Handle: RePEc:nbr:nberwo:10675
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    References listed on IDEAS

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    1. William N. Goetzmann & Alok Kumar, 2008. "Equity Portfolio Diversification," Review of Finance, European Finance Association, vol. 12(3), pages 433-463.
    2. Ning Zhu, 2002. "The Local Bias of Individual Investors," Yale School of Management Working Papers ysm272, Yale School of Management, revised 01 Sep 2009.
    3. Brad M. Barber & Terrance Odean, 2000. "Trading Is Hazardous to Your Wealth: The Common Stock Investment Performance of Individual Investors," Journal of Finance, American Finance Association, vol. 55(2), pages 773-806, April.
    4. French, Kenneth R & Poterba, James M, 1991. "Investor Diversification and International Equity Markets," American Economic Review, American Economic Association, vol. 81(2), pages 222-226, May.
    5. Blume, Marshall E & Friend, Irwin, 1975. "The Asset Structure of Individual Portfolios and Some Implications for Utility Functions," Journal of Finance, American Finance Association, vol. 30(2), pages 585-603, May.
    6. Marcin Kacperczyk & Clemens Sialm & Lu Zheng, 2005. "On the Industry Concentration of Actively Managed Equity Mutual Funds," Journal of Finance, American Finance Association, vol. 60(4), pages 1983-2011, August.
    7. JOSHUA D. COVAL & David Hirshleifer & TYLER G. SHUMWAY, 2004. "Can Individual Investors Beat the Market?," Finance 0412005, EconWPA.
    8. Joshua D. Coval & Tobias J. Moskowitz, 2001. "The Geography of Investment: Informed Trading and Asset Prices," Journal of Political Economy, University of Chicago Press, vol. 109(4), pages 811-841, August.
    9. Kelly, Morgan, 1995. "All their eggs in one basket: Portfolio diversification of US households," Journal of Economic Behavior & Organization, Elsevier, vol. 27(1), pages 87-96, June.
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    More about this item

    JEL classification:

    • D82 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Asymmetric and Private Information; Mechanism Design
    • G11 - Financial Economics - - General Financial Markets - - - Portfolio Choice; Investment Decisions

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