This study shows that U.S. individual investors hold under-diversified portfolios, where the level of under-diversification is greater among younger, low-income, less-educated, and less-sophisticated investors. The level of under-diversification is also correlated with investment choices that are consistent with over-confidence, trend-following behavior, and local bias. Furthermore, investors who over-weight stocks with higher volatility and higher skewness are less diversified. In contrast, there is little evidence that portfolio size or transaction costs constrains diversification. Under-diversification is costly to most investors, but a small subset of investors under-diversify because of superior information.

We examine whether corporate bankruptcies influence bank loan characteristics of geographically proximate firms. Controlling for industry contagion and local economic conditions, firms headquartered near a bankruptcy event experience a 7 basis point increase in loan spreads. The effect is transitory and cannot be fully explained by local correlated information or lenders’ financial health. Instead, the effect is more pronounced for informationally opaque bankruptcies and borrowers, and weakened among loans with relationship lenders and lenders with significant local presence.

We examine whether the trading activities of retail and institutional investors cause comovements in stock returns. Around stock splits, retail trading correlations (RTCs) decrease with stocks in the presplit price range and increase with stocks in the post-split price range. These shifts in RTCs induce changes in return comovements. In the cross section, return comovements among low-priced stocks are amplified when retail trades are more correlated and when aggregate uncertainty amplifies behavioral biases. We find similar patterns among local stocks and when firms change their corporate headquarters. In contrast to retail trading, institutional trading attenuates return comovements.