Retail bank runs are mostly a thing of the past. Every jurisdiction with a banking system has some form of deposit insurance, whether explicit or implicit. So, most customers can rest assured that they will be compensated even should their bank fail. But, while small and medium-sized depositors are extremely unlikely to feel the need to run, the same cannot be said for large short-term creditors (whose claims usually exceed the cap on deposit insurance). As we saw in the crisis a decade ago, when they are funded by short-term borrowing, not only are banks (and other intermediaries) vulnerable, the entire financial system becomes fragile.

This belated realization has motivated a large shift in the structure of bank funding since the crisis. Two complementary forces have been at work, one coming from within the institutions and the other from the authorities overseeing the system. This post highlights the biggest of these changes: the spectacular fall in uncollateralized interbank lending and the smaller, but still dramatic, decline in the use of repurchase agreements. The latter—also called repo—amounts to a short-term collateralized loan....