Business Economics · Role of money and interest rates in the economy

Money Supply and the Banking System: Credit Creation and the Money Multiplier

Updated 11 October 2026 · Fact-checked

Money supply is the stock of money held by the public. Banks create deposits by lending a fraction of what they receive and keeping a reserve. The simple money multiplier is 1 ÷ reserve ratio. The central bank controls supply through reserve requirements, policy rates and open market operations.

Understand Money Supply and the Banking System

Money is not only notes and coins. Most money in a modern economy is bank deposits. When you see a figure for money supply, it mostly counts deposits that the public can spend or convert to cash easily.

Banks work on a fractional reserve basis. They keep only a fraction of deposits as reserves (cash or balances with the central bank). They lend out the rest. They do this because depositors rarely withdraw everything on the same day.

Here is how credit creation works. A customer deposits ₹1,000. The bank keeps a part as reserve and lends the rest. The borrower spends the loan. The seller deposits the money in a bank. That bank again keeps a fraction and lends the rest. The process repeats. Each round is smaller than the last. Total deposits grow by a multiple of the original deposit.

The money multiplier measures this growth. In the simple model, it is 1 ÷ r, where r is the reserve ratio. If r = 10%, the multiplier is 10. A new ₹1,000 of reserves can support up to ₹10,000 of deposits. This is a maximum. It assumes banks lend all excess reserves, borrowers redeposit all the money, and the public holds no extra cash.

The central bank controls the base of this system. It can change the reserve requirement, change the rate at which it lends to banks, or buy and sell securities. In India, the RBI uses the cash reserve ratio (CRR), the statutory liquidity ratio (SLR) and the repo rate. A higher CRR or higher repo rate tends to reduce lending and money supply. A lower one tends to raise them. The effect is a tendency, not a fixed amount. It depends on banks' willingness to lend and on borrowers' demand.

Key rules to remember

Simple money multiplier: m = 1 ÷ r; r is the required reserve ratio as a decimal. Assumes no cash leakage and that banks hold no excess reserves.
Maximum deposit expansion: Total new deposits = initial new reserves × (1 ÷ r); Gives the maximum. It includes the initial deposit.
Maximum new lending: New loans created = initial deposit × (1 ÷ r) − initial deposit; Use when the question asks for loans, not deposits.
Money multiplier with cash holding: m = (1 + c) ÷ (c + r); c = currency held by public ÷ deposits; r = reserve ratio held against deposits. Money supply = m × monetary base.
Money supply from the base: M = m × H; H is the monetary base (high-powered money): currency plus bank reserves.
Excess reserves: Excess reserves = actual reserves − required reserves; Banks can lend only the excess. Required reserves = r × deposits.

How to solve Money Supply and the Banking System questions

Use this method for numerical and descriptive questions on credit creation and money supply.

1Identify what is asked: new deposits, new loans, the multiplier, or the change in money supply.
2Write down the reserve ratio r as a decimal. Check whether the question also gives a cash-holding ratio c.
3Choose the formula: m = 1 ÷ r for the simple case, or m = (1 + c) ÷ (c + r) when the public holds cash.
4Find the starting change: new deposit, new reserves, or change in the monetary base.
5Multiply by the multiplier. Then adjust: subtract the initial deposit if the question asks for loans only.
6State your assumptions in a line: no cash leakage, banks fully lend excess reserves, no excess reserves held.
7For descriptive parts, link the central bank tool to reserves, lending, deposits and then money supply, and note the limits of the effect.

Quickest way: Reserve ratio shortcut

When to use it: Use for MCQs and short numerical parts with a simple reserve ratio and no cash leakage.

Convert r to a multiplier: 1 ÷ r (10% gives 10; 20% gives 5; 25% gives 4).
Multiply by the new deposit or reserves for total deposits.
Subtract the initial deposit if the question asks for new loans.
If a CRR change is asked, a rise in r lowers the multiplier, so money supply falls.

Common mistakes in Money Supply and the Banking System

Using the multiplier as 1 × r instead of 1 ÷ r.
Students mix up the reserve ratio with the multiplier.
Fix: Check the direction: a smaller reserve ratio must give a larger multiplier.
Giving total deposits when the question asks for new loans.
The initial deposit is already in the banking system and is not a new loan.
Fix: Loans created = total deposit expansion − initial deposit. Read the question wording.
Treating the multiplier result as an exact outcome.
The simple formula gives a maximum under strict assumptions.
Fix: Say it is a maximum. Mention cash leakage, excess reserves and weak loan demand.
Saying banks lend out only what depositors have saved, as if deposits come first.
The loanable-funds picture is easier than the credit creation picture.
Fix: Explain that a loan creates a matching deposit. Reserve and capital limits constrain how much banks lend.
Mixing up CRR, SLR and repo rate.
All three are Indian policy terms that affect banks' lending capacity.
Fix: CRR is the share of deposits held as cash with the RBI. SLR is the share held in specified liquid assets. The repo rate is the rate at which the RBI lends to banks against securities.
Ignoring that a higher policy rate may not change money supply immediately.
Students assume a mechanical link.
Fix: Describe the chain: rate change, bank funding cost, lending rates, loan demand, deposits. Note time lags.

Worked examples

Example 1

A bank receives a new deposit of ₹2,00,000. The required reserve ratio is 20%. Banks hold no excess reserves and the public holds no cash. Find the maximum total increase in deposits and the maximum new loans created in the banking system.

Show the solution

r = 20% = 0.20.
Multiplier = 1 ÷ 0.20 = 5.
Maximum total increase in deposits = ₹2,00,000 × 5 = ₹10,00,000.
New loans = ₹10,00,000 − ₹2,00,000 = ₹8,00,000.
Check: reserves held = 20% × ₹10,00,000 = ₹2,00,000, which equals the initial deposit.

Answer: Maximum increase in deposits is ₹10,00,000. Maximum new loans are ₹8,00,000.

Example 2

The monetary base is ₹50,000 crore. The public holds currency equal to 25% of deposits (c = 0.25). Banks hold reserves of 15% of deposits (r = 0.15). Find the money multiplier and the money supply. Then explain what happens if the central bank raises the reserve ratio.

Show the solution

m = (1 + c) ÷ (c + r).
m = (1 + 0.25) ÷ (0.25 + 0.15) = 1.25 ÷ 0.40 = 3.125.
M = m × H = 3.125 × ₹50,000 crore = ₹1,56,250 crore.
If r rises, the denominator (c + r) rises, so m falls.
Banks must hold more reserves, so they can lend less per unit of base. Money supply tends to fall, other things equal.
Qualify: the effect depends on whether banks were holding excess reserves and on loan demand.

Answer: The multiplier is 3.125 and the money supply is ₹1,56,250 crore. A higher reserve ratio lowers the multiplier and tends to reduce money supply.

Exam tips

Write the formula first, then the numbers. Method marks depend on it.
State the assumptions behind the simple multiplier. Examiners look for them.
For central bank questions, give the chain of effects: tool, bank reserves or funding cost, lending, deposits, money supply.
Learn the definitions of CRR, SLR and repo rate in one line each. MCQs often test them.
Check whether the question asks for deposits, loans or money supply before you calculate.

Practice questions from Role of money and interest rates in the economy

Money Supply and the Banking System in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Money Supply and the Banking System: frequently asked questions

How do banks create money under fractional reserve banking?

A bank keeps a fraction of deposits as reserves and lends the rest. The loan is spent and ends up as a deposit in another bank. That bank lends again. Each round adds new deposits, so the banking system creates money.

What is the money multiplier formula?

In the simple model, it is 1 ÷ r, where r is the reserve ratio. With cash holding, use (1 + c) ÷ (c + r). Both give maximum values under stated assumptions.

How do CRR, SLR and the repo rate affect money supply?

A higher CRR leaves banks with less to lend, so credit tends to fall. A higher SLR also ties up more funds in liquid assets. A higher repo rate raises banks' funding costs and lending rates, which tends to reduce borrowing. Lower values work the other way.

Is the money multiplier always achieved in practice?

No. Banks may hold excess reserves, the public may hold cash, and borrowers may not want loans. The formula gives an upper limit, not a forecast.