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Portfolio Concentration and the Performance of Individual Investors

Zoran Ivkovich, Clemens Sialm () and Scott Weisbenner

No 10675, NBER Working Papers from National Bureau of Economic Research, Inc

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.

JEL-codes: D82 G11 (search for similar items in EconPapers)
Date: 2004-08
New Economics Papers: this item is included in nep-bec, nep-fin and nep-rmg
Note: AP
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Published as Ivkovi?, Zoran & Sialm, Clemens & Weisbenner, Scott, 2008. "Portfolio Concentration and the Performance of Individual Investors," Journal of Financial and Quantitative Analysis, Cambridge University Press, vol. 43(03), pages 613-655, September.

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