A model of competitive stock trading is developed in which investors are heterogeneous in their information and private investment opportunities and rationally trade for both informational and noninformational motives. The author examines the link between the nature of heterogeneity among...

This paper investigates the efficiency of household investment decisions using comprehensive disaggregated Swedish data. We consider two main sources of inefficiency: underdiversification ("down") and nonparticipation in risky asset markets ("out"). While a few households are very poorly...