Modigliani-Miller theorem

Understanding Bank Capital: A Primer

Over the past 40 years, U.S. capital markets have grown much faster than banks, so that banks’ share of credit to the private nonfinancial sector has dropped from 55% to 34% (see BIS statistics here).  Nevertheless, banks remain a critical part of the financial system. They operate the payments system, supply credit, and serve as agents and catalysts for a wide range of other financial transactions. As a result, their well-being remains a key concern. A resilient banking system is, above all, one that has sufficient capital to weather the loan defaults and declines in asset values that will inevitably come.

In this primer, we explain the nature of bank capital, highlighting its role as a form of self-insurance providing both a buffer against unforeseen losses and an incentive to manage risk-taking. We describe some of the challenges in measuring capital and briefly discuss a range of approaches for setting capital requirements. While we do not know the optimal level of capital that banks (or other intermediaries) should be required to hold, we suggest a practical approach for setting requirements that would promote the safety of the financial system without diminishing its efficiency....

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Making Finance Safe

Walter Wriston, Citicorp’s chief for nearly two decades until 1984, used to argue that banks’ didn’t need much, if any, capital. The global financial crisis put that view to rest. Today, we know that if banks are going to be able to absorb large unforeseen losses that would otherwise threaten financial stability, they need to finance themselves with equity, not just debt.

But how much capital do banks need to have to ensure the financial system is safe? Even after the financial crisis, answers to this question range widely, making it the single most contentious source of debate among bankers, regulators, and academics...

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