All Guts, No Glory: Trading and Diversification among Online Investors

I explore cross-sectional portfolio performance in a sample containing 324,736 transactions conducted by 16,831 investors at an Internet discount brokerage firm during the period May 1999 to March 2002. On average, investors hold undiversified portfolios, show a strong preference for risk, and trade aggressively. I measure performance using a panel data model, and explain the cross-sectional variation using investors’ turnover, portfolio size and degree of diversification. I find that turnover is harmful to performance due to fees, and is therefore more predominant among investors with small portfolios. It is argued that the degree of diversification is a proxy for investor skill, and it has a separate and distinct positive effect on performance. These findings are helpful in explaining the overall result that investors underperform the market by around 8.5% per year on average.