Business Economics · Money Market

Equilibrium in the Money Market: CA Foundation Business Economics

Updated 1 October 2026 · Fact-checked

Money market equilibrium is the interest rate at which the demand for money equals the supply of money. Supply is fixed by the central bank, so it is a vertical line. Demand slopes downward. Where they cross, the rate is set. Shift either curve and the rate changes.

Understand Equilibrium in the Money Market

Start with a simple idea. Money is an asset you can hold. Holding cash earns no interest. Holding bonds earns interest. So the interest rate is the cost of holding money: what you give up by keeping cash.

The demand for money falls as the interest rate rises. At a high rate, holding cash is costly, so people hold less and buy bonds. At a low rate, cash costs little to hold, so people hold more. This is why the money demand curve slopes downward. The interest rate is on the vertical axis and the quantity of money is on the horizontal axis.

The supply of money is decided mainly by the central bank (RBI in India) and the banking system. In the standard textbook diagram, supply is treated as fixed at a given time and does not depend on the interest rate. So it is drawn as a vertical line.

Equilibrium is where the demand curve cuts the supply line. That point gives the equilibrium interest rate. If the rate is above it, people want less money than exists. They buy bonds, bond prices rise and the rate falls. If the rate is below it, people want more money than exists. They sell bonds, bond prices fall and the rate rises. The rate moves back to equilibrium.

Now think about shifts. If the RBI increases money supply, the vertical line moves right and the interest rate falls. If it cuts money supply, the line moves left and the rate rises. If money demand rises (for example, income or prices rise), the demand curve shifts right and the rate rises. If money demand falls, the rate falls.

Key formulas to remember

Equilibrium condition: Md = Ms; The equilibrium interest rate is the rate at which the quantity of money demanded equals the quantity of money supplied.
Excess supply of money: Ms > Md → interest rate falls; People buy bonds, bond prices rise, and the rate moves down to equilibrium.
Excess demand for money: Md > Ms → interest rate rises; People sell bonds, bond prices fall, and the rate moves up to equilibrium.
Bond price and interest rate: Bond price ↑ ⇔ interest rate ↓; They move in opposite directions. Use this to explain the adjustment.
Direction of shifts: Ms ↑ → r ↓; Ms ↓ → r ↑; Md ↑ → r ↑; Md ↓ → r ↓; Holds when only one curve shifts and the other stays unchanged. If both shift, the result can be unclear.

How to solve Equilibrium in the Money Market questions

Use this method for any question on money market equilibrium or on a change in the interest rate.

1Identify what the question is about: the equilibrium rate, a gap between demand and supply, or a shift.
2Recall the shapes: money demand slopes downward; money supply is a vertical line set by the central bank.
3Find which curve is affected. Supply changes come from RBI action or bank lending. Demand changes come from income, price level or transactions.
4Decide the direction of the shift: right for an increase, left for a decrease.
5Read the new intersection. A rightward supply shift lowers the rate; a rightward demand shift raises it.
6If the question gives a rate away from equilibrium, compare Md and Ms to find excess demand or excess supply, then say which way the rate moves.
7Check that only one curve moved. If both moved, see which effect the question says is larger.
8Match your answer with the options and eliminate those that show the wrong direction.

Quickest way: Four-line shift check

When to use it: Use this for any MCQ that asks what happens to the interest rate after a change in money supply or money demand.

Ask: did the change hit supply or demand?
Supply up means rate down. Supply down means rate up.
Demand up means rate up. Demand down means rate down.
If the question gives a rate above or below equilibrium, say 'too much money' (rate falls) or 'too little money' (rate rises).
Cross out any option with the opposite direction. Usually two options go at once.
Skip a question only if you cannot tell which curve moved. Otherwise it is a quick mark.

Common mistakes in Equilibrium in the Money Market

Drawing money supply as a upward sloping curve in the basic model.
Students copy the goods market diagram, where supply slopes upward.
Fix: In this model the central bank fixes the money stock, so supply is a vertical line. It does not change with the interest rate.
Saying a rise in money supply raises the interest rate.
Students think more money means more of everything.
Fix: More money supply with unchanged demand means excess money. People buy bonds, and the rate falls.
Mixing up the direction of bond prices and interest rates.
Students learn the two facts separately and do not link them.
Fix: Remember they move opposite. When people buy bonds, prices go up and the rate goes down.
Shifting the demand curve when the interest rate changes.
Students confuse a movement along the curve with a shift.
Fix: A change in the interest rate moves you along the demand curve. Only other factors, such as income or the price level, shift it.
Confusing excess supply with excess demand at a given rate.
Students compare the wrong curve with the equilibrium point.
Fix: At a rate above equilibrium, demand is less than supply, so there is excess supply and the rate falls. At a rate below equilibrium, the reverse holds.

Worked examples

Example 1

The RBI increases the money supply while money demand stays unchanged. What happens to the equilibrium interest rate? (a) It rises (b) It falls (c) It stays unchanged (d) It first rises and then becomes zero

Show the solution

Identify the change: it affects supply, not demand.
An increase in supply shifts the vertical supply line to the right.
The demand curve is unchanged and slopes downward.
The new intersection is lower down the demand curve, so the interest rate is lower.
Check with the logic: people hold more money than they want, buy bonds, bond prices rise and the rate falls.

Answer: (b) It falls

Example 2

At a certain interest rate, the quantity of money demanded is less than the quantity supplied. What will happen? (a) Bond prices fall and the rate rises (b) Bond prices rise and the rate falls (c) The money supply curve shifts left (d) The money demand curve shifts right

Show the solution

Demand is less than supply, so there is excess supply of money.
People hold more money than they want, so they buy bonds.
Higher demand for bonds pushes bond prices up.
Bond prices and interest rates move in opposite directions, so the rate falls.
Options (c) and (d) describe curve shifts. Here the adjustment is a move along the curves, so they are wrong.

Answer: (b) Bond prices rise and the rate falls

Example 3

Income in the economy rises, which raises the demand for money, while money supply is unchanged. What happens to the equilibrium interest rate and the quantity of money held? (a) Rate rises, quantity held stays the same (b) Rate falls, quantity held rises (c) Rate rises, quantity held rises (d) Rate falls, quantity held falls

Show the solution

Higher income shifts the money demand curve to the right.
The supply line is vertical and has not moved.
The new demand curve cuts the vertical line at a higher point, so the rate rises.
Because the supply line is fixed, the quantity of money held in equilibrium equals the supply, which is unchanged.
So the rate rises and the quantity held stays the same.

Answer: (a) Rate rises, quantity held stays the same

Exam tips

Most questions test direction only. Learn the four shift results until they are automatic.
Always check whether the question describes a shift or a movement along a curve.
Remember the vertical supply line. Options that describe supply as responding to the interest rate in this model are usually traps.
Link bond prices and interest rates in your mind. Questions often use bond buying or selling to explain the adjustment.
With 0.25 negative marking, answer when you can name the curve that moved. Skip only if the wording is unclear.

Practice questions from Money Market

Equilibrium in the Money Market: frequently asked questions

How is the interest rate determined in the money market?

It is set where the demand for money equals the supply of money. Supply is fixed by the central bank, and demand falls as the rate rises. The crossing point gives the equilibrium rate.

What is the effect of an increase in money supply on the interest rate?

The supply line shifts right and the interest rate falls, if money demand stays the same. People hold extra money, buy bonds and push bond prices up. That lowers the rate.

Why is the money supply curve vertical?

In the basic model, the central bank decides the quantity of money, so it does not depend on the interest rate. A vertical line shows a fixed quantity at every rate.

Why does the money demand curve slope downward?

The interest rate is the cost of holding cash. When the rate is high, people hold less cash and more bonds. When it is low, they hold more cash.