超過準備金

Excess reserves are funds that commercial banks hold beyond any mandated minimum requirement. Banks hold them as a precautionary measure to prepare for unexpected events like large customer withdrawals. During economic uncertainty, banks also prefer holding reserves to mitigate concerns about borrowers defaulting, making it feel safer to retain these funds rather than lend them out.

The Federal Reserve uses Interest on Reserve Balances (IORB) to influence economic conditions. By increasing the IORB rate, the Fed encourages banks to hold reserves instead of lending, which slows economic activity. Lowering the IORB rate makes reserves less attractive, incentivizing banks to lend more and stimulate the economy through increased credit availability.

In the U.S., excess reserves are typically deposited with the Federal Reserve, where banks earn interest on them through the Interest on Reserve Balances program. This arrangement allows banks to maintain highly liquid funds while earning a return, balancing safety with profitability during uncertain economic periods.

Post-2008 financial reforms, including Basel III requirements like the Liquidity Coverage Ratio (LCR), require banks to maintain high-quality liquid assets to meet short-term obligations. These regulations transformed excess reserves from temporary buffers into permanent structural features of modern banking, making them essential for regulatory compliance and financial stability.

Excess reserves represent banks' deliberate strategic choice to prioritize secure, immediate access to funds over potential lending profits. During financial volatility or increased credit risk, institutions prefer holding surplus funds with the central bank rather than extending loans. This liquidity preference reflects the broader principle that safety and certainty often outweigh higher returns during uncertain times.

As of late 2025, the reserve requirement in the U.S. is zero, meaning banks have no mandated minimum reserves. Despite this, banks continue holding large excess reserves for precautionary reasons and to manage economic uncertainty, demonstrating that reserve holdings are driven by strategic risk management rather than regulatory mandates.

In a floor system, the IORB rate sets a lower boundary for short-term interest rates. When the IORB is high, banks retain reserves at the Federal Reserve, reducing credit supply and containing inflation. A lower IORB encourages lending, injecting liquidity into the economy and supporting economic growth through expanded credit availability.