4.6 Monetary Policy

Monetary policy is how a central bank, like the Federal Reserve, moves interest rates to shift aggregate demand and steer the economy toward full employment and price stability. Use expansionary policy to close a recessionary gap and contractionary policy to close an inflationary gap.

Policy Rate AP Macro Definition

In AP Macroeconomics, a policy rate is the interest rate a central bank targets to influence borrowing, spending, investment, and aggregate demand. In the United States, the policy rate is the federal funds rate, the overnight interbank lending rate.

The key AP distinction is reserves. In a limited-reserves system, the central bank changes the money supply through tools like open-market operations. In an ample-reserves system, like the current U.S. system, the central bank changes administered rates such as interest on reserves.

Why This Matters for the AP Macroeconomics Exam

Monetary policy shows up across the financial sector material because it ties together money, interest rates, and aggregate demand. You can be asked to choose the correct policy action for a given output gap, show the change on a money market, reserve market, or AD-AS graph, and trace the cause and effect chain from a policy move to real GDP and the price level. Balance sheet and money multiplier calculations also connect here, especially in a limited reserves setting. The free-response section often asks you to pick the right open-market operation and explain it, so reading the scenario carefully and answering only what is asked matters more than listing every tool you know.

Key Takeaways

• Expansionary policy lowers interest rates to raise aggregate demand and close a recessionary gap; contractionary policy raises interest rates to lower aggregate demand and close an inflationary gap.
• The tools and how they work depend on the banking system: limited reserves works through changing the money supply, ample reserves works through administered interest rates.
• The U.S. banking system has ample reserves, and the Fed's key policy tool is interest on reserves.
• The federal funds rate is the overnight interbank lending rate the Fed targets as its policy rate.
• In a limited reserves system, an open-market purchase or sale changes the money supply by more than the monetary base because of the money multiplier.
• Monetary policy works with lags, so it does not produce instant results.

What Monetary Policy Is

Monetary policy refers to actions taken by a central bank, which in the United States is the Federal Reserve, to influence interest rates and aggregate demand and achieve goals such as price stability and full employment.

Expansionary vs. Contractionary

There are two directions for monetary policy.

Expansionary monetary policy (also called easy monetary policy) is used when the economy is in a recessionary gap. The goal is to lower interest rates, stimulate investment and consumption, and increase real GDP.

Contractionary monetary policy (also called tight monetary policy) is used when the economy is in an inflationary gap. The goal is to raise interest rates, reduce investment and consumption, and decrease real GDP.

The specific tools the Fed uses and how they work depend on whether the banking system has limited reserves or ample reserves, which is an important distinction in AP Macroeconomics.

Limited Reserves vs. Ample Reserves

The tools of monetary policy and the way they are implemented differ depending on which environment a banking system operates in.

In an economy with limited reserves, banks hold just enough reserves to meet requirements, so the money supply is sensitive to changes in reserves. The central bank influences interest rates mainly by changing the money supply through open-market operations and adjustments to the reserve requirement.

In an economy with ample reserves, banks hold far more reserves than required. Because reserves are abundant, changes in the money supply do not effectively change the nominal interest rate. Instead, the central bank influences the nominal interest rate by changing its administered interest rates, which are rates the central bank sets directly, such as the interest rate paid on reserves.

The banking system in the United States has ample reserves, and the Federal Reserve's key policy tool is interest on reserves.

Many central banks carry out policy to hit a target range for an overnight interbank lending rate, sometimes called the central bank's policy rate. In the United States, this is the federal funds rate, the rate at which banks lend reserves to each other overnight.

Tools of Monetary Policy

The tools of monetary policy include the central bank's discount rate and other administered interest rates (such as interest on reserves), open-market operations, and the required reserve ratio.

Tools in a Limited Reserves Economy

In an economy with limited reserves, the central bank mainly uses these tools to change the money supply, which in turn changes the nominal interest rate.

The discount rate is the interest rate the Federal Reserve charges commercial banks to borrow reserves directly from the Fed. Lowering the discount rate makes borrowing cheaper for banks, encouraging them to borrow more and increasing the money supply. Raising it has the opposite effect.

The reserve ratio (reserve requirement) is the percentage of demand deposits that banks must hold in reserve and cannot lend. Raising the reserve ratio decreases excess reserves and reduces the money supply. Lowering it increases excess reserves and expands the money supply.

Open-market operations involve buying and selling government bonds. When the Fed buys bonds, it pays with new money that enters the banking system, increasing reserves and the monetary base. When the Fed sells bonds, money leaves the banking system, decreasing reserves and the monetary base. In an economy with limited reserves, the money multiplier amplifies the effect, so the change in the money supply is greater than the change in the monetary base.

Tools in an Ample Reserves Economy (The U.S. Today)

In an economy with ample reserves, open-market operations and reserve requirements are less effective because banks already hold excess reserves far beyond what is required. Changes in the money supply do not effectively move the interest rate.

Instead, the central bank influences the nominal interest rate by adjusting its administered interest rates.

Interest on reserves (IOR) is the interest rate the Federal Reserve pays banks on reserves held at the Fed. This is the Fed's primary policy tool in the current ample-reserves environment. When the Fed raises IOR, banks demand a higher return before lending, which pushes the federal funds rate up. When the Fed lowers IOR, the federal funds rate falls. The IOR effectively sets a floor for the federal funds rate because no bank would lend reserves to another bank at a rate below what the Fed pays.

The discount rate still functions as a ceiling, since banks would not borrow from each other at a rate above what the Fed charges directly.

Calculating the Effects of Monetary Policy

Working through balance sheets and calculations is a key part of monetary policy analysis. Here is a worked example.

Example: Open-Market Purchase in a Limited Reserves Economy

Suppose the Fed conducts an open-market purchase of $100 million of government bonds from commercial banks.

Step 1: What happens to reserves and the monetary base? The Fed pays for the bonds by crediting $100 million to the banks' reserve accounts. Reserves increase by $100 million, and the monetary base increases by $100 million.

Step 2: Bank balance sheet effect (immediately after the purchase):

The bank swapped one asset (bonds) for another asset (reserves). Total assets are unchanged, and liabilities are unchanged.

Step 3: Apply the money multiplier. In a limited-reserves system, banks will lend out their new excess reserves, and through the deposit creation process the money supply expands by more than the initial change in reserves. The simple money multiplier is:

$\text{Money Multiplier} = \frac{1}{\text{Required Reserve Ratio}}$

If the required reserve ratio is 10% (0.10):

$\text{Money Multiplier} = \frac{1}{0.10} = 10$

Step 4: Calculate the maximum change in the money supply.

$\Delta \text{Money Supply} = \Delta \text{Reserves} \times \text{Money Multiplier} = \$100 \text{ million} \times 10 = \$1 \text{ billion}$

So the maximum increase in the money supply from a $100 million open-market purchase is $1 billion.

Example: Open-Market Sale

If the Fed instead sells $100 million of government bonds, reserves decrease by $100 million, the monetary base decreases by $100 million, and using the same 10% reserve ratio, the maximum decrease in the money supply is:

$\$100 \text{ million} \times 10 = \$1 \text{ billion}$

The key point is that in a limited-reserves system, the effect on the money supply is greater than the effect on the monetary base because of the money multiplier. Open-market purchases increase the monetary base and expand the money supply; open-market sales decrease the monetary base and contract the money supply.

The Reserve Market Model

Three models can be used to show the short-run effects of monetary policy: the money market model, the reserve market model, and the AD-AS model.

The reserve market model graphs the market for bank reserves.

• The horizontal axis shows the quantity of reserves.
• The vertical axis shows the federal funds rate (the overnight interbank lending rate).
• Demand for reserves slopes downward, since at lower federal funds rates banks are willing to hold more reserves and lend less in the interbank market.
• Supply of reserves is determined by the central bank.

In a limited reserves environment, the supply curve is vertical (fixed quantity of reserves), and shifts in supply move the equilibrium federal funds rate, just like shifts in money supply move the interest rate in the money market model.

In an ample reserves environment, the supply of reserves is so large that the demand curve is nearly flat at the rate the Fed pays on reserves (IOR). The Fed shifts interest rates not by changing the quantity of reserves but by changing its administered rates, which moves the flat portion of the demand curve up or down.

Effects of Monetary Policy

Monetary policy is the Federal Reserve's way of correcting the economy when it is in a recessionary gap or an inflationary gap. Expansionary policy is used to close a recessionary gap; contractionary policy is used to close an inflationary gap.

In a Limited Reserves Economy

In a limited reserves environment, the transmission works through the money supply.

Expansionary policy (recessionary gap): The Fed increases the money supply (for example, an open-market purchase), the nominal interest rate falls, investment and consumption increase, aggregate demand increases, and real GDP rises back toward full employment.

What this looks like on the graphs: In the reserve market model, an open-market purchase shifts the supply of reserves to the right, which lowers the equilibrium federal funds rate. In the money market model, the money supply curve shifts to the right, lowering the nominal interest rate. The lower interest rate stimulates investment and interest-sensitive consumption, so in the AD-AS model the aggregate demand (AD) curve shifts to the right. This increases both real output and the price level in the short run, helping to close the recessionary gap.

Contractionary policy (inflationary gap): The Fed decreases the money supply (for example, an open-market sale), the nominal interest rate rises, investment and consumption decrease, aggregate demand decreases, and real GDP falls back toward full employment.

What this looks like on the graphs: In the reserve market model, an open-market sale shifts the supply of reserves to the left, which raises the equilibrium federal funds rate. In the money market model, the money supply curve shifts to the left, raising the nominal interest rate. The higher interest rate discourages investment and interest-sensitive consumption, so in the AD-AS model the AD curve shifts to the left. This decreases both real output and the price level in the short run, helping to close the inflationary gap.

In an Ample Reserves Economy (The U.S. Today)

In an ample reserves environment, the transmission works through administered interest rates.

Expansionary policy (recessionary gap): The Fed lowers its administered interest rates (for example, lowers interest on reserves), the federal funds rate falls, investment and consumption increase, aggregate demand increases, and real GDP rises back toward full employment.

What this looks like on the graphs: In the reserve market model, lowering the IOR shifts the flat portion of the demand and supply floor downward, reducing the federal funds rate. In the AD-AS model, lower interest rates increase investment and consumption, shifting the AD curve to the right. Real output increases and the price level rises in the short run.

Contractionary policy (inflationary gap): The Fed raises its administered interest rates (for example, raises interest on reserves), the federal funds rate rises, investment and consumption decrease, aggregate demand decreases, and real GDP falls back toward full employment.

What this looks like on the graphs: In the reserve market model, raising the IOR shifts the floor upward, increasing the federal funds rate. In the AD-AS model, higher interest rates reduce investment and consumption, shifting the AD curve to the left. Real output decreases and the price level falls in the short run.

In both environments, monetary policy influences interest rates, aggregate demand, real output, and the price level. The difference is how the central bank moves interest rates: through money supply changes (limited reserves) or through administered rate changes (ample reserves).

Lags in Monetary Policy

In reality, there are lags to monetary policy caused by the time it takes to recognize a problem in the economy and the time it takes the economy to adjust to the policy action. These lags mean that monetary policy does not produce instant results and can sometimes take effect after economic conditions have already changed.

How to Use This on the AP Macroeconomics Exam

Free Response

When a question gives you an output gap, name the correct policy direction first. Recessionary gap calls for expansionary policy; inflationary gap calls for contractionary policy. Then identify the specific tool that fits the scenario. If the question is about a limited reserves system, an open-market purchase increases the money supply and an open-market sale decreases it. If the question is about the U.S. ample reserves system, the lever is interest on reserves or another administered rate.

Common Trap

When asked which open-market operation is appropriate, give only the one correct action and explain it. Listing every possible tool, or naming both a purchase and a sale, signals that you are guessing and can cost points. Answer exactly what the question asks.

Problem Solving

For balance sheet and money multiplier questions in a limited reserves setting, find the change in reserves first, then multiply by the simple money multiplier of one over the required reserve ratio. Remember that this gives the maximum change in the money supply, and that the real-world change is usually smaller because banks may hold excess reserves and people may hold more currency.

Graphing

Practice linking the models. A single policy action should move the reserve market or money market graph and then carry through to the AD-AS graph. Show the interest rate change first, then the shift in aggregate demand, then the effect on real output and the price level. Label every axis and curve, and use arrows to show the direction of each shift.

Common Misconceptions

• Monetary policy and fiscal policy are not the same. Monetary policy is run by the central bank through interest rates and the money supply, while fiscal policy is run by the government through spending and taxes.
• In the current U.S. system, the Fed does not move rates by changing the quantity of reserves. With ample reserves, changes in the money supply do not effectively move the interest rate, so the Fed adjusts administered rates like interest on reserves instead.
• The money multiplier result is a maximum, not a guaranteed amount. Banks holding excess reserves or the public holding more currency makes the actual change smaller.
• An open-market purchase is expansionary, not contractionary. Buying bonds adds reserves and increases the money supply; selling bonds drains reserves and decreases it.
• Lower interest rates do not directly raise real GDP. They work through investment and consumption, which then shift aggregate demand, which then affects real output and the price level.
• Monetary policy is not instant. Recognition and adjustment lags mean effects can arrive after conditions have already shifted.

Related AP Macroeconomics Guides

• 4.1 Financial Assets
• 4.3 Definition, Measurement, and Functions of Money
• 4.4 Banking and the Expansion of the Money Supply
• 4.2 Nominal vs. Real Interest Rates
• 4.5 The Money Market
• 4.7 The Loanable Funds Market