The heterogeneous reactions of household debt to income shocks

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.