Portfolio Concentration and the Performance of Individual Investors

52 Pages Posted: 2 Sep 2004 Last revised: 3 Sep 2010

See all articles by Zoran Ivkovich

Zoran Ivkovich

Michigan State University, Department of Finance

Clemens Sialm

University of Texas at Austin - McCombs School of Business; National Bureau of Economic Research (NBER); AQR Capital Management, LLC

Scott J. Weisbenner

University of Illinois at Urbana-Champaign - Department of Finance; National Bureau of Economic Research (NBER)

Multiple version iconThere are 2 versions of this paper

Date Written: August 2004

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

Ivkovich, Zoran and Sialm, Clemens and Weisbenner, Scott J., Portfolio Concentration and the Performance of Individual Investors (August 2004). NBER Working Paper No. w10675. Available at SSRN: https://ssrn.com/abstract=579818

Zoran Ivkovich

Michigan State University, Department of Finance ( email )

315 Eppley Center
East Lansing, MI 48824-1122
United States

Clemens Sialm (Contact Author)

University of Texas at Austin - McCombs School of Business ( email )

Austin, TX 78712
United States

HOME PAGE: http://faculty.mccombs.utexas.edu/Clemens.Sialm/

National Bureau of Economic Research (NBER)

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

AQR Capital Management, LLC ( email )

Greenwich, CT
United States

Scott J. Weisbenner

University of Illinois at Urbana-Champaign - Department of Finance ( email )

340 Wohlers Hall, MC-706
1206 S. Sixth Street
Champaign, IL 61820
United States
217-333-0872 (Phone)
217-244-9867 (Fax)

HOME PAGE: http://business.illinois.edu/weisbenn/

National Bureau of Economic Research (NBER) ( email )

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

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