Monetary Tightening and U.S. Bank Fragility in 2023: Mark-to-Market Losses and Uninsured Depositor Runs?
by Erica Jiang, Gregor Matvos, Tomasz Piskorski, and Amit Seru
We analyze U.S. banks’ asset exposure to a recent rise in the interest rates with implications for financial stability. The U.S. banking system’s market value of assets is $2.2 trillion lower than suggested by their book value of assets accounting for loan portfolios held to maturity. Marked-to-market bank assets have declined by an average of 10% across all the banks, with the bottom 5th percentile experiencing a decline of 20%. Most of these asset declines were not hedged by banks with use of interest rate derivatives. We illustrate in a simple model that uninsured leverage (i.e., Uninsured Debt/Assets) is the key to understanding whether these losses would lead to some banks in the U.S. becoming insolvent ‒ unlike insured depositors, uninsured depositors stand to lose a part of their deposits if the bank fails, potentially giving them incentives to run. We show that a bank’s survival depends on the market beliefs about the share of uninsured depositors who will withdraw money following a decline in the market value of bank assets. If interest rate increases are small such that the bank’s decline in asset values is relatively small, there is no risk of a run equilibrium. However, for sufficiently high increases in interest rates, we have multiple equilibria in which uninsured depositor run making banks insolvent (i.e., a “bad” run equilibrium) becomes a possibility. Banks with smaller initial capitalization and higher uninsured leverage have a smaller range of beliefs supporting a “good” no run equilibrium, increasing their fragility to uninsured depositor runs. A case study of the recently failed Silicon Valley Bank (SVB) is illustrative. 10 percent of banks have larger unrecognized losses than those at SVB. Nor was SVB the worst capitalized bank, with 10 percent of banks having lower capitalization than SVB. On the other hand, SVB had a disproportional share of uninsured funding: only 1 percent of banks had higher uninsured leverage. Combined, losses and uninsured leverage provide incentives for an SVB uninsured depositor run. We compute similar incentives for the sample of all U.S. banks. Even if only half of uninsured depositors decide to withdraw, almost 190 banks with assets of $300 billion are at a potential risk of impairment, meaning that the mark-to-market value of their remaining assets after these withdrawals will be insufficient to repay all insured deposits. If uninsured deposit withdrawals cause even small fire sales, substantially more banks are at risk. Regions with lower household incomes and large shares of minorities are more exposed to the bank risk. We also show that decline in banks’ asset values eroded the ability of banks to withstand adverse credit events – focusing on commercial real estate loans. Overall, these calculations suggest that recent declines in bank asset values very significantly increased the fragility of the US banking system to uninsured depositor runs.
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