Vulnerable Banks

by Robin Greenwood, Augustin Landier & David Thesmar

Overview — Since the beginning of the US financial crisis in 2007, regulators in the United States and Europe have been frustrated by the difficulty in identifying the risk exposures at the largest and most levered financial institutions. Yet, at the time, it was unclear how such data might have been used to make the financial system safer. This paper is an attempt to show simple ways in which this information can be used to understand how deleveraging scenarios could play out. To do so the authors develop and test a model to analyze financial sector stability under different configurations of leverage and risk exposure across banks. They then apply the model to the largest financial institutions in Europe, focusing on banks' exposure to sovereign bonds and using the model to evaluate a number of policy proposals to reduce systemic risk. When analyzing the European banks in 2011, they show how a policy of targeted equity injections, if distributed appropriately across the most systemic banks, can significantly reduce systemic risk. The approach in this paper fits into, and contributes to, a growing literature on systemic risk. Key concepts include:

This model can simulate the outcome of various policies to reduce fire sale spillovers in the midst of a crisis.
Size caps, or forced mergers among the most exposed banks, do not reduce systemic risk very much.
However, modest equity injections, if distributed appropriately between the most systemic banks, can cut the vulnerability of the banking sector to deleveraging by more than half.
The model can be adapted to monitor vulnerability on a dynamic basis using factor exposures.

Author Abstract

When a bank experiences a negative shock to its equity, one way to return to target leverage is to sell assets. If asset sales occur at depressed prices, then one bank's sales may impact other banks with common exposures, resulting in contagion. We propose a simple framework that accounts for how this effect adds up across the banking sector. Our framework explains how the distribution of bank leverage and risk exposures contributes to a form of systemic risk. We compute bank exposures to system-wide deleveraging, as well as the spillover of a single bank's deleveraging onto other banks. We show how our model can be used to evaluate a variety of crisis interventions, such as mergers of good and bad banks and equity injections. We apply the framework to European banks vulnerable to sovereign risk in 2010 and 2011.