Macroprudential regulation under repo funding

The use of collateral has become one of the most widespread risk mitigation techniques. While it brings stabilizing effects to the individual cash lender, it may exacerbate systemic risk by accelerating bank deleveraging under funding stress. We show how a liquidity shock to the cash lender may propagate as a solvency shock via liquidity hoarding even if the cash lender remains solvent in all states of nature. Albeit a privately optimal response of the cash lender to a liquidity shock, bank deleveraging may lead to excessive bankruptcy among its borrowing counterparties while, at the same time, triggering contagion across asset classes. To buttress financial system resilience, we lay out a menu of macroprudential policies that deactivate this channel of financial contagion.