A monetary operating framework in which the central bank supplies reserves abundantly, so the overnight market rate settles at or near the rate paid on reserves rather than being steered by marginal scarcity. Policy is set by adjusting the administered floor rate, not by fine-tuning reserve quantity.
How it works
With reserves abundant relative to demand, banks have no incentive to lend overnight below the rate they earn on reserves (IORB in the US, the deposit facility rate at the ECB), so that administered rate becomes a "floor" anchoring the overnight rate. The central bank moves policy by changing the floor, decoupling rate control from balance-sheet size — contrast with a corridor system, where rates are kept between facilities by managing scarce reserves.
Why it matters now
The ECB's 2024-2025 operational framework review converged on a demand-driven floor system, and the Fed continues to operate an ample-reserves floor while running QT toward an as-yet-undefined "ample" level — making the floor-versus-corridor question central to how far balance-sheet runoff can go before money-market rates lose their anchor.
Example
After the 2008 crisis the Federal Reserve shifted to a floor system: with reserves swollen by QE, it set the effective federal funds rate by adjusting the interest-on-reserves rate (IORB) rather than by open-market scarcity. In March 2024 the ECB announced its review would steer EONIA's successor €STR near the deposit facility rate via a demand-driven floor, retaining a broad balance sheet.
Frequently asked
- What is a floor system in monetary policy?
- A floor system is a central-bank operating framework where reserves are supplied abundantly, pinning the overnight rate at or near the administered rate paid on reserves. The central bank sets policy by moving that floor rate — IORB
Glossary · IORB
IORB is the rate the Federal Reserve pays banks on balances held in their master accounts. It is the Fed's primary administered tool for steering the federal funds rate, setting an effective floor under money-market rates by making reserves a risk-free yielding asset.
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Glossary · deposit facility rate
The interest rate the European Central Bank pays commercial banks on overnight deposits parked at the Eurosystem. As the floor of the ECB's three-rate corridor, it anchors the lower bound of money-market rates and, under a floor system, effectively sets the policy stance for short-term euro funding.
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- How does a floor system differ from a corridor system?
- A floor system anchors the overnight rate to the administered deposit rate by keeping reserves abundant, whereas a corridor system
Glossary · the corridor
The corridor is the band between a central bank's standing lending rate (ceiling) and deposit rate (floor), within which the overnight money-market rate trades. In a corridor system the policy rate sits in the middle; the width and symmetry of the band shape interbank price discovery and reserve scarcity.
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- Why does the floor-versus-corridor question matter for QT?
- The floor system lets a central bank run quantitative tightening while still controlling rates, but only until reserves stop being abundant. As the Fed drains reserves toward an undefined 'ample' level, the floor risks losing its anchor and rates drifting toward scarcity — which is why money-market spreads and repo rates are watched closely during runoff.
- Why did the Federal Reserve adopt a floor system after 2008?
- The Federal Reserve adopted a floor system after 2008 because quantitative easing swelled reserves far beyond what a scarcity-based corridor could manage. With reserves abundant, the Fed steers the effective federal funds rate by adjusting the interest-on-reserves rate (IORB) rather than through open-market scarcity, gaining the authority to pay interest on reserves in 2008.
- Does a floor system require a large central-bank balance sheet?
- Yes, a floor system requires a balance sheet large enough to keep reserves abundant relative to bank demand, since the anchor depends on banks holding more reserves than they strictly need. The ECB's 2024 framework retained a broad balance sheet for exactly this reason, supplying reserves through structural portfolios and refinancing operations.