Money Demand vs Money Supply
Money Demand and Money Supply are two Money & Monetary Policy concepts in AP Economics that students often mix up. Money demand is the amount of wealth people choose to hold as money rather than in interest-bearing assets. The money supply is the total amount of money circulating in an economy, including cash and checkable deposits. Here is how they compare side by side.
It slopes downward against the nominal interest rate, which is the opportunity cost of holding money. People hold money for transactions and as a precaution. Money demand shifts with the price level and real GDP.
Central banks influence it through open market operations, the reserve requirement, and the discount rate. Common measures are M1 (most liquid) and M2 (broader). Changes in the money supply affect interest rates and aggregate demand.
Money Demand vs Money Supply: What Sets the Nominal Interest Rate
| Money demand | Money supply | |
|---|---|---|
| What it shows | How much money people want to hold at each interest rate | The quantity of money in circulation |
| Slope | Downward sloping | Vertical, set by the central bank |
| Why that slope | A higher interest rate raises the opportunity cost of holding cash | The central bank fixes the quantity regardless of the interest rate |
| Shifted by | The price level, real GDP, and payment technology | Central bank action: open market operations, the discount rate, reserve policy |
| Effect of an increase | The nominal interest rate rises | The nominal interest rate falls |
| Which rate it determines | The NOMINAL rate, not the real rate | The NOMINAL rate, not the real rate |
Why money demand slopes down
Holding money means holding something that pays no interest. The cost of doing so is the interest you gave up by not holding a bond instead, so the nominal interest rate IS the opportunity cost of holding money. When rates are high, people economise on cash and move funds into interest-bearing assets, so quantity of money demanded falls. When rates are low, holding cash costs little and people hold more. That is the entire reason for the downward slope, and stating it in those words is often a rubric row on its own. Build the diagram at /sandbox/monetary-policy.
The supply curve is vertical because the central bank draws it there
Money supply is shown as a vertical line because the central bank sets the quantity and does not adjust it in response to the interest rate. Buying bonds through open market operations pays banks by crediting their reserve accounts, which increases the money supply and shifts the line right, and the equilibrium nominal interest rate falls. Selling bonds does the reverse. This is the first step of the monetary policy transmission chain, and a full-credit answer continues it: the lower rate encourages investment and interest-sensitive consumption, which shifts aggregate demand right. Two diagrams, connected by one sentence.
Nominal, not real, and do not confuse this with loanable funds
The money market determines the NOMINAL interest rate. The loanable funds market, where saving supplies funds and borrowing demands them, determines the REAL interest rate. They are different diagrams answering different questions, and mixing them is a reliable way to lose points: government borrowing belongs in loanable funds, central bank bond purchases belong in the money market. Also note that a change in the price level shifts money DEMAND, not supply, because higher prices mean people need more money for the same transactions. See /glossary/compare/real-interest-rate-vs-nominal-interest-rate for the two rates themselves.
Frequently asked questions
What determines the nominal interest rate?
The intersection of money demand and money supply in the money market. Money demand slopes down because a higher interest rate raises the opportunity cost of holding cash; money supply is vertical because the central bank sets the quantity. Where they meet is the equilibrium nominal interest rate.
What shifts money demand?
The price level, real GDP, and changes in payment technology. Higher prices or higher real output mean more transactions, so people need to hold more money at any interest rate and demand shifts right. Easier electronic payments reduce the cash people need to hold and shift it left.
What is the difference between the money market and loanable funds?
The money market determines the nominal interest rate through the supply and demand for money, and the central bank controls the supply. The loanable funds market determines the real interest rate through saving and borrowing, and it is where government deficits cause crowding out. Using the wrong diagram is a common and costly exam error.
Live Money Market graph. Drag the curves, or open the full version.
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