Many debt claims, such as bonds, are resaleable; others, such as repos, are not. There was a fivefold increase in repo borrowing before the 2008–2009 financial crisis. Why? Did banks’ dependence on non-resaleable debt precipitate the crisis? In this paper, we develop a model of bank lending with credit frictions. The key feature of the model is that debt claims are heterogenous in their resaleability. We find that decreasing credit market frictions leads to an increase in borrowing via non-resaleable debt. Such borrowing has a dark side: It causes credit chains to form, because, if a bank makes a loan via non-resaleable debt and needs liquidity, it cannot sell the loan but must borrow via a new contract. These credit chains are a source of systemic risk, as one bank’s default harms not only its creditors but also its creditors’ creditors. Overall, our model suggests that reducing credit market frictions may have an adverse effect on the financial system and even lead to the failures of financial institutions.

We develop a model in which collateral serves to protect creditors from the claims of other creditors. We find that, paradoxically, borrowers rely most on collateral when pledgeability is high. This is when taking on new debt is easy, which dilutes existing creditors. Creditors thus require collateral for protection against possible dilution by collateralized debt. There is a collateral rat race. But collateralized borrowing has a cost: it encumbers assets, constraining future borrowing and investment. There is a collateral overhang. Our results suggest that policies aimed at increasing the supply of collateral can backfire, triggering an inefficient collateral rat race. Likewise, upholding the absolute priority of secured debt can exacerbate the rat race.

We develop a theory of banking that explains why banks started out as commodities warehouses. We show that warehouses become banks because their superior storage technology allows them to enforce the repayment of loans most effectively. Further, interbank markets emerge endogenously to support this enforcement mechanism. Even though warehouses store deposits of real goods, they make loans by writing new fake warehouse receipts, rather than by taking deposits out of storage. Our theory helps to explain how modern banks create funding liquidity and why they combine warehousing (custody and deposit-taking), lending, and private money creation within the same institutions. It also casts light on a number of contemporary regulatory policies.