Daniel P. Murphy

We study how household debt portfolios-aggregated at the ZIP code level-respond to local income shocks in the United States. We implement two separate identification strategies: (i) a Bartik-style instrument that shifts local earnings via national industry trends, and (ii) a novel instrument utilizing the timing and location of shale oil and gas well discoveries. Across both designs, positive income shocks are, on average, associated with deleveraging. This average, however, masks a sharp bifurcation in financial behavior. Deleveraging in total credit is driven by financially healthier households-those with higher credit scores, higher incomes, or lower leverage-who restrain the growth of credit-card and auto debt. In contrast, financially vulnerable households often treat the windfall as a gateway to new auto credit while still deleveraging credit-card and typically mortgage debt. Looking at mixed-profile households, we find strong mortgage leveraging among households with high income and high debt or low credit scores. These results show that the same income shock can trigger balance-sheet repair for some households and additional leverage for others-varying by both borrower type and debt category-underscoring substantial underlying heterogeneity and highlighting barriers to broad-based financial stability.