We derive a measure that captures the extent to which common ownership shifts managers’ incentives to internalize externalities. A key feature of the measure is that it allows for the possibility that not all investors are attentive to whether a manager's actions benefit the investor's overall portfolio. Empirically, we show that potential drivers of common ownership, including mergers in the asset management industry and, under certain circumstances, even indexing, could diminish managerial motives to internalize externalities. Our findings illustrate the importance of accounting for investor inattention when analyzing whether the growth of common ownership affects managerial incentives.

Using individual credit bureau data matched with cash windfalls from fracking, we estimate that windfall recipients reduce debt-to-income by 2.4 percentage points relative to no-windfall controls. Debt repayment effects are 3 times stronger for subprime individuals than for prime individuals. Based on the timing of upfront versus continuing cash payments, debt repayment coincides with the timing of payments but not with news about future payments. These findings present a challenge for purely forward-looking models of debt. Indeed, when we incorporate a windfall shock into a forward-looking model, the model predicts an increase in debt that runs counter to our evidence of debt repayment.