Fractional Reserve Banking Explained: Money Creation & Risks

Banks face bankruptcy risk due to maturity mismatch - they accept short-term deposits (which depositors can withdraw anytime) but make long-term loans (which borrowers repay over time). If many depositors simultaneously demand withdrawals (a bank run), the bank may not have enough liquid reserves to pay everyone. This is why banks must maintain adequate reserves and why bank runs can cause insolvency even for solvent banks.

Banks face a fundamental structural challenge: savers want immediate access to deposits while borrowers need long-term loans for investments. This maturity mismatch creates vulnerability during financial crises. When crises occur, depositors rush to withdraw funds (bank runs), potentially causing bank failures. Diamond and Dybvig proposed solutions including deposit insurance (government-guaranteed payouts during crises) and government financial support for banks. These mechanisms help prevent self-fulfilling prophecies of bank failures and maintain systemic stability.

Banks operate on a dangerous maturity mismatch by borrowing short-term (even overnight) from the interbank lending market while lending long-term to clients, creating systemic vulnerability; this model became evident during the 2007-2008 financial crisis when LIBOR rates spiked dramatically as banks lost confidence in each other, nearly causing the entire banking system to collapse. The system requires continuous low interest rates and debt accumulation to function, making it inherently unstable and prone to future crises when confidence in short-term funding markets erodes.

Banking crises are fundamentally caused by maturity mismatch - when banks borrow short-term funds (like overnight deposits) to purchase long-term assets (like mortgages or bonds), creating vulnerability when lenders demand repayment or refuse to roll over loans; this structural fragility, combined with opacity in financial instruments and herd behavior during crises, explains why seemingly small losses can trigger massive systemic failures, as demonstrated by the 2008 financial crisis where all five major U.S. investment banks faced similar core issues despite different failure timelines.

A bank run occurs when depositors lose confidence and withdraw funds simultaneously. With a 10% reserve ratio, each dollar withdrawn requires banks to reduce $10 in checking account money. Banks face maturity mismatch: they borrow short-term (deposits can be withdrawn instantly) but lend long-term (mortgages lasting 30 years). This structural instability requires central bank intervention to prevent bank failures.

The Ministry of Finance's Banking Bureau was replaced by the Financial Services Agency (金融庁) in 2000, marking a shift from strict regulatory control to 'prudential policy' (プルーデンス政策). This approach emphasizes encouraging banks to take prudent actions through competition rather than direct regulation. The Basel Accords established international capital adequacy standards: Basel I (1988) required 8% capital for international banks; Basel II (2007) allowed internal models but recognized the 'procyclicality problem' where capital requirements could amplify economic cycles; Basel III (2013) addressed this by introducing countercyclical capital buffers. Early intervention measures allow regulators to take action before banks fail. Deposit insurance (預金保険制度), established in 1971, protects depositors by guaranteeing deposits up to 10 million yen when banks fail, reducing the incentive for bank runs while maintaining financial stability.

Banking regulation ensures banks maintain sufficient capital to meet risks, as banks collect short-term deposits but lend long-term, creating fund rotation where total loans exceed capital. Regulation minimizes bank default probability, protecting the entire financial system and economy. Without regulation, banks take excessive risks due to deposit insurance, which protects depositors even if banks fail. This creates moral hazard where banks become aggressive lenders. Governments must control bank capital to prevent systemic risk, where failure of one bank can trigger cascading failures across interconnected financial institutions. Before 1988, each country had different capital requirements, creating regulatory arbitrage. The Basel Committee was formed in 1988 with 12 countries to develop uniform international standards. The accord established that banks' assets to capital ratio should be less than 20%, meaning capital to total assets should be greater than 5%. The major innovation was the capital adequacy ratio considering total credit exposure including off-balance sheet items. For on-balance sheet items, risk weights reflect credit risk: cash and government securities have 0% weight, claims on banks have 20%, uninsured mortgages have 50%, and corporate bonds have 100%. For off-balance sheet items, a credit equivalent amount is computed. The accord required 8% capital of risk-weighted assets, divided into Tier 1 (equity, minimum 2% of RWA) and Tier 2 (subordinate debt, minimum 50% of total capital). The G30 policy recommendations emerged in the 1990s, providing 20 risk management recommendations for derivatives dealers. Key recommendations included clear risk management policies approved by senior management and boards, daily marking to market of derivatives positions, and consistent market risk measurement using Value at Risk (VaR). Risk management functions must be completely independent from trading operations. Credit exposures from derivative trading must consider both current replacement value and projected future exposure. Netting agreements, typically through ISDA Master Agreements, reduce overall credit exposure by treating all transactions with a counterparty as a single transaction upon default.

Deposit insurance protects depositors up to limits (e.g., $250,000 in the US) during bank failures but creates moral hazard where banks take excessive risks knowing depositors are protected. Mitigation strategies include higher premiums for risky banks, stricter regulations, and capital requirements. Banks must maintain capital to absorb potential losses during extreme events. Economic capital (estimated by banks) typically exceeds regulatory capital (mandated by Basel Norms). Basel I focused on credit risk, Basel II added market risk, and Basel III incorporated operational risk. Capital serves as a cushion for rare but severe events, ensuring banks can continue operating and meet obligations even under stress.

The Basel Accords represent a progressive evolution of international banking regulations designed to strengthen financial stability: Basel I (1988) introduced the 8% capital adequacy ratio with credit risk focus; Basel II (2004-2010) expanded to cover operational and market risks through a three-pillar framework (minimum capital requirements, supervisory review, and market discipline); and Basel III (2013-present) further strengthened requirements by introducing leverage ratios and liquidity coverage ratios (LCR and NSFR) to address the limitations exposed by the 2008 financial crisis, ensuring banks maintain sufficient high-quality capital and liquid assets to withstand external shocks.

Basel III is a post-2008 financial crisis banking regulation that requires banks to hold minimum capital based on risk levels, serving as a safety net to absorb losses and prevent systemic failures; however, its implementation faces significant debate between regulators seeking financial stability and banks concerned about reduced lending capacity, with the US currently reconsidering proposals due to political and economic concerns.

The traditional multiplier theory (banks lend reserves, creating deposits that become new reserves for other banks) is descriptively false. Banks do not lend reserves directly; they assess their liquidity position and determine how much they can lend based on expected reserve drains. Banks estimate reserve drains from interbank payments and can recapture reserves through interbank lending. The actual process is much more complex than the mechanistic multiplier model suggests. The Bank of England's 2014 paper on money creation in the modern economy is descriptively and accountably valid but is often misused to support extreme conclusions about unlimited money creation.

The theory of endogenous versus exogenous money has been debated among economists for over 100 years. Endogenous money theory posits that money supply is determined by banks through credit creation, not directly by central banks. Modern consensus, as stated by central banks worldwide, supports endogenous money: for a given amount of base money, banks can create more or less money through lending decisions. Central banks directly control two types of money: physical cash and bank reserves (electronic accounts of commercial banks at the central bank). However, commercial banks create the majority of money supply through credit expansion. When banks make loans, they create new money through accounting entries, not by distributing existing central bank money. This is why central banks control interest rates to influence credit creation, not the total money supply directly. The broader money supply (M1, M2) is the result of bank lending behavior, not direct central bank control.

Banks create money endogenously through lending without printing physical currency. When a bank grants a loan, it simultaneously creates a new deposit for the borrower and a corresponding asset on its books. This creates new money from nothing through accounting entries. The credit multiplier effect describes how a single unit of physical money can generate a much larger volume through the banking system. When someone deposits money, banks lend out fractions, which get redeposited and lend again, multiplying the money supply many times over. This entire system operates through accounting entries rather than physical cash, fundamentally changing how money is created and distributed in modern economies.

According to Modern Monetary Theory (TMM), commercial banks create money endogenously through the lending process, where granting a loan simultaneously creates a deposit in the borrower's account, rather than the central bank creating money exogenously first; this challenges the traditional 'money multiplier' model and explains how banks function as intermediaries that create purchasing power from credit extensions, with the central bank serving as a 'lender of last resort' to maintain system stability.

The money multiplier is an endogenous variable, not controlled by policymakers. Textbooks suggest a multiplier of 10 based on reserve requirements, but the actual multiplier has fallen to approximately 3 and continues declining. This occurs because as economies become more indebted, risk premiums rise, making it harder for banks to profitably employ reserves. The Bruner-Meltzer equation shows that while the Fed can inject reserves, utilization depends on private sector willingness and ability to use them profitably. Additionally, velocity of money falls in highly indebted economies, further limiting monetary policy effectiveness. These endogenous constraints explain why monetary policy faces diminishing returns.