Faculty & Research

This paper documents a link between trading and diversification by using detailed trading records from a Swedish discount broker matched to individual tax records. Investors’ diversification is measured by stake size, defined as the fraction of their risky financial wealth invested in individual stocks at the broker under study. High stake investors have concentrated portfolios, trade more, and achieves lower trading performance. They share several features with those who trade excessively: they have lower income, wealth, age, and education, suggesting that they lack investment expertise. The results directly imply that trading losses in the cross- section mainly are borne by those who can least afford them.