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The '''cash reserve ratio''', also called the reserve requirement ratio, is the minimum fraction of deposits that a bank is required to hold as reserves, either as cash in its vaults or as balances at the central bank. It is a regulatory instrument that affects the ability of banks to create credit, and it has been used as a tool of monetary policy and of prudential regulation. In many economies the requirement has been reduced or eliminated, but it remains important in some and it continues to influence the behaviour of banks.

== Definition and operation ==

The cash reserve ratio is expressed as a percentage of a bank's deposits or of a broader measure of its liabilities, and it determines the minimum reserves that the bank must hold. The reserves may be held as vault cash, as balances at the central bank, or as a combination, depending on the regulations. Banks that hold more than the required amount hold excess reserves, and those that hold less must obtain reserves from other banks or from the central bank.

The requirement is enforced by the central bank, which monitors compliance and imposes penalties for shortfalls. The ratio may apply to all deposits or only to certain categories, and it may vary across types of institution. The design of the requirement, including its coverage and its level, determines its effect on the banking system and on the money supply.

== Role in monetary policy ==

Historically, the cash reserve ratio was a principal instrument of monetary policy, because it determined the relationship between reserves and the money supply. An increase in the ratio reduced the money multiplier and contracted credit, while a decrease expanded it. The instrument was used alongside open market operations and the discount rate to manage liquidity and to influence economic activity.

The effectiveness of the instrument depends on the behaviour of banks and on the demand for loans. If banks hold excess reserves or if the demand for credit is weak, changes in the ratio may not translate into changes in lending, and the effect on the money supply is muted. The instrument is also blunt, affecting all banks and all borrowers, and it can disrupt the functioning of markets. For these reasons, many central banks have moved to interest rate policy and have reduced or eliminated reserve requirements.

== Prudential and liquidity functions ==

The cash reserve ratio also serves prudential and liquidity purposes. By requiring banks to hold a buffer of liquid assets, it reduces the risk that a bank will be unable to meet withdrawals, and it supports the stability of the banking system. The requirement provides a cushion against shocks and complements other prudential requirements, such as capital and liquidity rules.

The prudential function has become more prominent as the monetary role has diminished. Liquidity coverage ratios and net stable funding requirements have been introduced to address liquidity risk more comprehensively, and reserve requirements complement these by providing a minimum buffer. The design of the requirements must balance the objective of stability against the cost to banks and the effect on their profitability and lending.

== International variation and reform ==

The use of the cash reserve ratio varies widely across countries. Some central banks maintain significant requirements and use them actively, while others have reduced them to low levels or eliminated them. The variation reflects differences in the monetary framework, in the development of financial markets, and in the reliance on other instruments.

Reforms have reduced the role of the instrument in many economies. The move to interest rate targeting, the growth of interbank markets, and the development of alternative instruments have all contributed to the decline. At the same time, reserve requirements have been used as a macroprudential tool, adjusted to manage credit growth and to address risks in specific sectors, and their role has evolved rather than disappeared.

== Determination and Operation ==
The cash reserve ratio is set by the central bank and applies to specified categories of deposits. In many systems the requirement is calculated as an average over a maintenance period, so that temporary fluctuations in deposits or reserves can be smoothed. Banks hold required reserves either as balances at the central bank, as vault cash, or both, depending on the jurisdiction.

The ratio differs across deposit types in some systems. Demand deposits, which are more volatile, may carry a higher requirement than time deposits. In other systems a uniform ratio applies. Where the central bank pays interest on reserves, the effective cost of the requirement is the difference between the policy rate and the interest paid, and this can be adjusted to influence bank behaviour.

== Role in Monetary Policy ==
Changes in the cash reserve ratio alter the money multiplier. Raising the ratio reduces the amount of deposits that can be supported by a given quantity of reserve money, contracting credit and the money supply. Lowering the ratio has the opposite effect. Because a change affects all banks simultaneously and immediately, the instrument is powerful but blunt, and it can disrupt bank balance sheets and liquidity management.

In practice, many central banks prefer open market operations and standing facilities to fine-tune liquidity, using reserve requirements mainly for structural or prudential purposes. Price-based instruments allow more precise and continuous adjustment than the discrete steps typical of reserve ratio changes.

== Prudential and Macroprudential Uses ==
Beyond monetary policy, reserve requirements serve prudential and macroprudential ends. They ensure a buffer of liquid assets and can be tightened to restrain credit growth and systemic risk. In some emerging economies the reserve ratio has been used actively as a countercyclical tool, raised during credit booms and lowered during downturns. The instrument can be targeted by currency or by institution type, which makes it flexible but also complex to administer.

== Evolution in Modern Systems ==
Recent decades have seen a decline in the use of active reserve requirements in several advanced economies, partly because central bank liquidity management has become more sophisticated and partly because interest on reserves has become the primary tool for steering short-term rates. Some jurisdictions have reduced or eliminated reserve requirements altogether, relying instead on ample reserves supplied through the central bank's balance sheet. Emerging markets, by contrast, continue to use the instrument, often in combination with other tools, because of its direct effect on credit conditions.

== See also ==

* [[Reserve Requirement]]
* [[Monetary Base]]
* [[Money Multiplier]]
* [[Bank Liquidity]]
* [[Central Bank]]

== References ==

<ref name="r1">Central bank publications on reserve requirements.</ref>
<ref name="r2">Bank for International Settlements work on monetary instruments.</ref>
<ref name="r3">International Monetary Fund analyses of monetary policy.</ref>
<ref name="r4">Journal literature on reserve requirements and credit.</ref>

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[[Category:Central banking]]
[[Category:Monetary economics]]
[[Category:Banking]]