Economic theory suggests that households should invest their financial wealth in a combination of cash and a well-diversified equity portfolio. Yet, many households' equity investments are strongly concentrated in a few assets. Attempts to explain this discrepancy have included low levels of...

Household investment mistakes are an important concern for researchers and policymakers alike; portfolio underdiversification ranks among those mistakes that are potentially most costly. However, its roots and empirical importance are poorly understood. I estimate quantitatively meaningful...