The Money Market

Understand how the supply and demand for money determine the nominal interest rate and shape monetary policy decisions.

AP Macroeconomics

What Is Money?

In economics, money is any asset that is widely accepted as a medium of exchange, a unit of account, and a store of value. The money market focuses on the supply and demand for liquid money balances: the cash and checking deposits people choose to hold.

Medium of Exchange

Accepted to buy goods and services

Unit of Account

Common measure of value for pricing

Store of Value

Retains purchasing power over time

Why People Hold Money

Holding money is convenient but comes at a cost: you forgo the interest you could earn on bonds or savings. Economists identify three motives for holding money:

1

Transaction motive: Everyday purchases require liquid cash or deposits.

2

Precautionary motive: People keep reserves for unexpected expenses.

3

Speculative motive: When interest rates are low, bonds look less attractive, so people hold more money.

The Money Market Graph

Money Supply: Set by the Fed

The money supply (MS) is a vertical line because the Federal Reserve controls it through monetary policy. It does not depend on the interest rate. The Fed uses three main tools:

1

Open Market Operations (OMO): Buying or selling government bonds to change reserves in the banking system.

2

Discount Rate: The interest rate the Fed charges banks for short-term loans. Lowering it encourages borrowing.

3

Reserve Requirement: The fraction of deposits banks must hold. Lowering it increases the money multiplier.

Money Demand: Why It Slopes Down

The money demand curve (MD) is downward-sloping because of the opportunity cost of holding money. When interest rates are high, holding cash means forgoing lucrative bond returns, so people demand less money. When rates are low, bonds pay little, so people prefer liquidity.

Shift vs. Movement Along

Shift of MD

The entire curve moves left or right. Caused by changes in price level, real GDP, or financial technology. At every interest rate, the quantity demanded changes.

Movement Along MD

A move up or down the existing curve. Caused only by a change in the nominal interest rate. The curve itself stays put.

Finding Equilibrium

Equilibrium in the money market occurs where MS intersects MD. At this point, the quantity of money people want to hold equals the quantity the Fed has supplied. The resulting interest rate is the equilibrium nominal interest rate \( r^* \).

1

If \( r \) is above \( r^* \): People want to hold less money than supplied. They buy bonds, pushing bond prices up and interest rates down toward \( r^* \).

2

If \( r \) is below \( r^* \): People want to hold more money than supplied. They sell bonds, pushing bond prices down and interest rates up toward \( r^* \).

How to Analyze a Money Market Shift

1

Identify the event: Is it changing money supply (Fed action) or money demand (GDP, price level, technology)?

2

Determine the direction: Does the affected curve shift right (increase) or left (decrease)?

3

Find the new equilibrium: Where the shifted curve meets the unchanged curve is the new \( r^* \).

4

State the result: Did the nominal interest rate rise or fall? What are the downstream effects on investment, AD, and real GDP?

Example: Expansionary Monetary Policy

Example: Contractionary Monetary Policy

Example: Increase in Money Demand

The Transmission Mechanism

Changes in the money market ripple through the economy via a clear chain of events. This is the monetary transmission mechanism:

Common Mistakes

✕ Sloping the MS Curve

Money supply is vertical. It does not respond to interest rates: the Fed sets it at a fixed quantity.

✕ Confusing Shift vs. Movement

A change in income shifts MD. A change in the interest rate causes movement along MD, not a shift.

✕ Wrong Axis Labels

The vertical axis is the nominal interest rate, not the real interest rate or price level. On the AP exam, mislabeling costs points.

Summary Table

	Expansionary Policy	Contractionary Policy
Fed Action	Buys bonds / Lowers discount rate	Sells bonds / Raises discount rate
MS Shift	Right (increase)	Left (decrease)
Interest Rate	Falls	Rises
Investment	Increases	Decreases
AD / Real GDP	Increases	Decreases
Used When	Recession / High unemployment	Inflation / Overheating economy

Question 1 of 5

The money demand curve is downward-sloping because:

The opportunity cost of holding money is the interest forgone on bonds. When the interest rate rises, holding money becomes more expensive, so the quantity demanded decreases: this gives MD its downward slope.

Question 2 of 5

If the Federal Reserve conducts an open market purchase, which of the following occurs in the money market?

An open market purchase means the Fed buys government bonds, injecting reserves into the banking system. This increases the money supply (MS shifts right), creating a surplus of money at the old rate, which drives the nominal interest rate down.

Question 3 of 5

An increase in real GDP will cause which change in the money market?

Higher real GDP means more transactions, so people need more money at every interest rate. This shifts MD right. With MS unchanged (the Fed didn't act), the increased demand for money pushes the nominal interest rate up.

Question 4 of 5

The money supply curve in the money market is vertical because:

The Fed determines the quantity of money in the economy through its policy tools. Since this quantity does not change in response to the interest rate, the money supply curve is a vertical line at whatever quantity the Fed has chosen.

Question 5 of 5

If the nominal interest rate is above the equilibrium rate in the money market, which of the following will happen?

When the interest rate is above equilibrium, people hold less money than is supplied. They use the excess money to buy bonds, which drives bond prices up. Since bond prices and interest rates move inversely, the interest rate falls back toward \( r^* \).