The Foreign Exchange Market - AP Macroeconomics

SECTION 1

Historical Context & Motivation

International trade requires a mechanism for converting one nation's currency into another, and the foreign exchange market (often abbreviated forex or FX) fills that role. Today, the forex market is the largest financial market in the world, with daily turnover exceeding $7.5 trillion. Understanding how exchange rates are determined is essential for analyzing trade balances, capital flows, and the international transmission of monetary and fiscal policy—all core topics on the AP Macroeconomics exam.

1944 • Bretton Woods Agreement

Allied nations established a system of fixed exchange rates pegged to the U.S. dollar, which was convertible to gold at $35 per ounce. The IMF and World Bank were created to stabilize the system.

1971 • Nixon Shock

President Nixon suspended dollar-gold convertibility, effectively ending Bretton Woods and initiating the transition toward floating exchange rates.

1973 • Era of Managed Floats

Major economies adopted flexible exchange rate regimes in which currency values were primarily determined by market forces, though central banks occasionally intervened.

1999 • Launch of the Euro

Eleven European Union members adopted a common currency, the euro (€), eliminating bilateral exchange rates among participants and creating the world's second-most-traded currency.

2020s • Modern FX Markets

Electronic trading, algorithmic strategies, and the rise of emerging-market currencies have made forex the most liquid market on Earth, operating 24 hours a day across global financial centers.

The central question this lesson addresses is straightforward but powerful: what determines the price of one currency in terms of another, and how do shifts in economic policy, relative interest rates, and trade patterns cause that price to change? These questions lie at the heart of the AP Macroeconomics open-economy framework.

SECTION 2

Core Principles & Definitions

Before analyzing supply and demand in the forex market, you need a precise vocabulary. The concepts below form the foundation for every graph, equation, and free-response question you will encounter on the AP exam.

Exchange Rate

The price of one currency expressed in units of another. For example, if $1 = ¥110, the dollar's exchange rate against the yen is 110. On AP graphs, the vertical axis shows the price of the currency being analyzed in terms of the other currency.

Appreciation & Depreciation

Appreciation means a currency's value rises relative to another (it buys more foreign currency). Depreciation means it falls. These terms apply to flexible-rate systems; under fixed rates, the analogous terms are revaluation and devaluation.

Demand for a Currency

Demand for a currency arises from foreigners who want to buy that country's goods, services, or financial assets. An increase in demand shifts the demand curve rightward and causes the currency to appreciate.

Supply of a Currency

Supply comes from domestic residents who exchange their currency for foreign currency to purchase foreign goods, services, or assets. An increase in supply shifts the supply curve rightward and causes the currency to depreciate.

Equilibrium Exchange Rate

The rate at which the quantity of a currency demanded equals the quantity supplied. In a purely flexible system, this equilibrium is determined solely by market forces without government intervention.

SECTION 3

The Foreign Exchange Market Graph

The AP Macroeconomics exam frequently asks you to draw and analyze a standard supply-and-demand diagram for a currency. The diagram below depicts the market for the U.S. dollar. The vertical axis measures the price of one dollar expressed in euros (€/ $), and the horizontal axis measures the quantity of dollars exchanged per period. The downward-sloping demand curve (D$ ) reflects the fact that as the dollar becomes cheaper in euro terms, European buyers find American goods and assets more affordable, so they demand more dollars. The upward-sloping supply curve (S$) reflects that as the dollar appreciates, American buyers find European goods cheaper in dollar terms, so they supply more dollars to acquire euros.

The equilibrium exchange rate e₁ is determined at point E where the supply of dollars (S

, cyan) intersects the demand for dollars (D

, violet). At any rate above e₁, there is a surplus of dollars, pushing the rate down; at any rate below e₁, there is a shortage, pushing the rate up.

Notice the labeling conventions that the AP exam expects. The vertical axis must clearly state the currency whose market is being graphed, expressed as foreign currency per unit of domestic currency (here, € per $). The demand curve represents all foreign entities wanting to purchase dollars, while the supply curve represents all domestic entities willing to sell dollars. Shifts in these curves—driven by changes in tastes, relative incomes, relative price levels, relative interest rates, or speculation—are the primary analytical tools tested on the exam.

SECTION 4

Determinants of Exchange Rates

On the AP exam, you must be able to explain why a currency's supply or demand curve shifts. The key determinants fall into several categories. Changes in these determinants shift either the demand curve or the supply curve, altering the equilibrium exchange rate and quantity.

1. Changes in Relative Interest Rates

If the U.S. raises its real interest rate relative to other countries, foreign investors seek higher returns by purchasing U.S. financial assets. This increases the demand for dollars and simultaneously decreases the supply of dollars (because American investors are less inclined to move money abroad). The dollar appreciates. This is the most frequently tested determinant on the AP exam because it links monetary policy directly to the exchange rate.

2. Changes in Relative Price Levels (Inflation)

If the U.S. experiences higher inflation than its trading partners, American goods become relatively more expensive. Foreign demand for U.S. exports falls, reducing demand for dollars. At the same time, Americans buy more (now relatively cheaper) foreign imports, increasing the supply of dollars. Both effects cause the dollar to depreciate.

3. Changes in Relative Income / GDP Growth

If U.S. national income grows faster than foreign income, Americans import more goods, increasing the supply of dollars on the forex market. This causes the dollar to depreciate. Conversely, faster foreign income growth boosts demand for U.S. exports and thus demand for dollars.

4. Changes in Tastes and Expectations

A shift in consumer preferences toward foreign goods increases the supply of the domestic currency (and vice versa). Similarly, speculation about future exchange rate movements can trigger large capital flows that shift demand or supply curves in anticipation.

INTEREST RATE PARITY (CONCEPTUAL)

If r_US > r_Foreign → D\$ ↑, S\$ ↓ → Dollar appreciates

Where r represents the real interest rate. Higher domestic real interest rates attract foreign financial capital, increasing demand for the domestic currency and reducing its supply on the forex market.

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AP Exam Tip

SECTION 5

Shifts in the Forex Market & Policy Linkages

The AP exam frequently tests how monetary and fiscal policy changes in one country ripple through the forex market and affect the trade balance. The diagram below illustrates what happens when the Federal Reserve raises the federal funds rate, increasing U.S. real interest rates relative to the rest of the world.

When U.S. real interest rates rise, foreign investors increase their demand for dollars (D

₁ → D

₂), and American investors reduce capital outflows, decreasing the supply of dollars (S

₁ shifts left to S

₂). The equilibrium moves from E₁ to E₂, and the dollar appreciates from e₁ to e₂.

Determinant Change	Effect on D$	Effect on S$	Dollar Exchange Rate
U.S. real interest rate ↑	D$ ↑ (shifts right)	S$ ↓ (shifts left)	Appreciates
U.S. inflation rises (relative)	D$ ↓ (shifts left)	S$ ↑ (shifts right)	Depreciates
U.S. income growth ↑	No direct effect	S$ ↑ (shifts right)	Depreciates
Foreign demand for U.S. goods ↑	D$ ↑ (shifts right)	No direct effect	Appreciates
Speculation: expected $ depreciation	D$ ↓ (shifts left)	S$ ↑ (shifts right)	Depreciates

Summary of exchange rate determinants tested on the AP exam

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Key takeaway

POLICY CHAIN

SECTION 6

Worked Example: Fiscal Policy & the Exchange Rate

Consider a classic AP FRQ scenario: the U.S. government increases government spending (expansionary fiscal policy) while the Federal Reserve holds the money supply constant. Trace the effects through the loanable funds market, the forex market, and the trade balance.

Worked example

1
Step 1 — Identify the Policy Change

The U.S. government increases spending, financed by borrowing. This increases the demand for loanable funds in the U.S. loanable funds market, shifting the demand curve for loanable funds to the right.
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Step 2 — Determine the Effect on Real Interest Rates

With the money supply held constant and increased government borrowing, the real interest rate in the U.S. rises. The new equilibrium in the loanable funds market occurs at a higher rate.

U.S. real interest rate increases
3
Step 3 — Trace to the Forex Market

Higher U.S. real interest rates attract foreign financial capital. Foreign investors demand more dollars to purchase U.S. bonds and other financial assets. The demand for dollars in the forex market increases (D$ shifts right). Simultaneously, U.S. investors have less incentive to invest abroad, so the supply of dollars decreases (S$ shifts left).

D$ increases and S$ decreases → dollar appreciates
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Step 4 — Determine the Effect on Net Exports

A stronger dollar makes U.S. exports more expensive for foreign buyers and foreign imports cheaper for American consumers. Exports decrease, imports increase, and the trade balance moves toward deficit (net exports fall).

Net exports decrease (NX ↓)
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Step 5 — Note the Crowding-Out Effect

The decline in net exports partially offsets the increase in aggregate demand from government spending. This international crowding-out effect supplements the domestic crowding out of investment that occurs through higher interest rates, reducing the overall multiplier effect of the fiscal expansion.

Fiscal policy is less effective in an open economy

SECTION 7

Fixed vs. Flexible Exchange Rate Systems

Countries choose between exchange rate regimes that range from a completely fixed (pegged) system to a freely floating system, with various managed arrangements in between. The AP exam expects you to understand the trade-offs inherent in each regime and how central bank intervention operates under fixed rates.

Feature	Fixed Exchange Rate	Flexible Exchange Rate
Rate determination	Government or central bank sets the rate and commits to maintaining it	Market supply and demand determine the rate continuously
Central bank role	Must buy/sell foreign reserves to maintain the peg	No obligation to intervene (though may do so occasionally under a managed float)
Monetary policy independence	Severely limited—interest rates must serve the exchange rate target	Fully independent—monetary policy can target domestic inflation and employment
Exchange rate volatility	Low day-to-day volatility, but risk of sudden crisis if reserves run out	Continuous small adjustments; may have short-run volatility
Terminology	Revaluation (official increase) / Devaluation (official decrease)	Appreciation (market increase) / Depreciation (market decrease)

Comparison of exchange rate regimes

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Key takeaway

THE TRILEMMA

SECTION 8

Connecting Exchange Rates to the Current Account

The forex market does not exist in isolation; it is the mirror image of the balance of payments. Every transaction that creates demand for a currency on the forex market corresponds to a credit in that country's balance of payments, and every transaction that creates supply corresponds to a debit. The AP exam links the forex market to the current account (trade in goods, services, and income) and the financial (capital) account (trade in financial assets).

Concept	Basic Forex Analysis	Advanced Balance of Payments View
Dollar appreciation	Demand for $ exceeds supply → exchange rate rises	Financial account surplus (capital inflow) finances a current account deficit
Trade deficit	Imports > Exports → net outflow of domestic currency	Current account deficit = Financial account surplus (net capital inflow)
Key identity	Market clears at equilibrium exchange rate	Current Account + Financial Account = 0 (excluding statistical discrepancy)

BALANCE OF PAYMENTS IDENTITY

Current Account + Financial Account = 0

A current account deficit must be financed by a financial account surplus (net capital inflow), and vice versa. This identity reinforces why exchange rate changes caused by interest rate differentials simultaneously affect trade flows.

Looking ahead, more advanced courses in international economics explore purchasing power parity (PPP), the real exchange rate versus the nominal exchange rate, and the Marshall-Lerner condition. For the AP exam, the crucial skill is the ability to trace a complete causal chain from a policy change through the loanable funds market, to the forex market, and ultimately to the effect on net exports and aggregate demand.

SECTION 9

Practice Problems

Question 1: CONCEPTUAL

If the European Central Bank raises its benchmark interest rate while the Federal Reserve holds U.S. rates constant, what is the expected effect in the market for U.S. dollars?

A. The demand for dollars increases, and the dollar appreciates.
B. The supply of dollars increases and the demand for dollars decreases, and the dollar depreciates.
C. The supply of dollars decreases, and the dollar appreciates.
D. Both the demand for and supply of dollars increase, and the effect on the exchange rate is indeterminate.

Show answer (B)

B is correct. Higher European interest rates attract capital to Europe. American investors supply more dollars to the forex market to purchase euro-denominated assets (S$ shifts right), and European investors reduce their demand for dollars since domestic returns are now more attractive (D$ shifts left). Both shifts cause the dollar to depreciate. A is wrong because higher foreign rates reduce, not increase, demand for dollars. C is wrong because the supply of dollars increases rather than decreases. D is wrong because supply increases but demand decreases, so the direction of the exchange rate change is determinate—the dollar depreciates.

Question 2: BASIC CALCULATION

If the exchange rate changes from $1 = ¥120 to $1 = ¥100, which of the following is true?

A. The dollar appreciated, and Japanese goods became more expensive for Americans.
B. The dollar depreciated, and American goods became cheaper for Japanese consumers.
C. The dollar depreciated, and American goods became more expensive for Japanese consumers.
D. The yen depreciated, and Japanese goods became cheaper for Americans.

Show answer (B)

B is correct. The dollar now buys fewer yen (120 → 100), so the dollar has depreciated and the yen has appreciated. When the dollar depreciates, U.S. goods become relatively cheaper for foreign buyers because they need fewer yen to obtain each dollar. A is wrong because the dollar depreciated (it buys fewer yen). C is wrong because depreciation makes American goods cheaper, not more expensive, for foreigners. D is wrong because the yen appreciated (not depreciated) and Japanese goods became more expensive, not cheaper, for Americans.

Question 3: INTERMEDIATE

Country A adopts expansionary fiscal policy (increased government spending) with no change in monetary policy. Assuming a flexible exchange rate and free capital mobility, which sequence correctly traces the international effects?

A. Government spending ↑ → real interest rate ↑ → capital inflow ↑ → currency appreciates → net exports ↓
B. Government spending ↑ → real interest rate ↓ → capital outflow ↑ → currency depreciates → net exports ↑
C. Government spending ↑ → real interest rate ↑ → capital outflow ↑ → currency depreciates → net exports ↑
D. Government spending ↑ → real interest rate ↑ → capital inflow ↑ → currency depreciates → net exports ↓

Show answer (A)

A is correct. Increased government borrowing raises the real interest rate in the loanable funds market. Higher domestic rates attract foreign capital (capital inflow), increasing demand for the domestic currency, which appreciates. An appreciated currency makes exports more expensive and imports cheaper, so net exports fall. B is wrong because expansionary fiscal policy raises, not lowers, real interest rates when the money supply is unchanged. C is wrong because higher domestic rates attract capital inflow, not outflow. D is wrong because capital inflow causes appreciation, not depreciation.

Question 4: APPLIED

Assume the United States and the United Kingdom operate under flexible exchange rates with free capital mobility. The Bank of England unexpectedly raises its policy interest rate. (a) Draw a correctly labeled graph of the foreign exchange market for the British pound (£), showing the effect of this change. Label the initial equilibrium E₁ and the new equilibrium E₂. (b) Based on your graph, did the pound appreciate or depreciate? Explain. (c) What is the expected effect on U.S. net exports to the UK? Explain.

Show answer

(a) The graph should have the price of the pound in dollars per pound ($/£) on the vertical axis and the quantity of pounds on the horizontal axis. The demand for pounds shifts rightward (from D₁ to D₂) because U.S. investors want to buy UK assets offering higher returns, and the supply of pounds shifts leftward (from S₁ to S₂) because UK investors have less incentive to purchase foreign assets. The new equilibrium E₂ is above E₁. (b) The pound appreciated. The higher UK interest rate attracted foreign financial capital into the UK, increasing demand for pounds and decreasing supply, driving up the pound's exchange rate. (c) U.S. net exports to the UK increase. Because the pound appreciated (equivalently, the dollar depreciated against the pound), American goods are now relatively cheaper for British consumers, increasing U.S. exports to the UK.

Question 5: CRITICAL THINKING

The United States is experiencing a recession. In response, the Federal Reserve conducts open-market purchases of government bonds. (a) What is the immediate effect on the nominal interest rate in the money market? Explain. (b) Using a correctly labeled graph of the foreign exchange market for the U.S. dollar, show the effect of the Federal Reserve's action on the exchange rate. Identify the initial and new equilibrium. (c) Explain the effect on U.S. net exports. (d) Explain how the change in net exports reinforces or counteracts the Federal Reserve's goal of fighting the recession. (e) Suppose instead that the United States maintained a fixed exchange rate. Explain why the Federal Reserve's ability to conduct this expansionary monetary policy would be limited.

Show answer

(a) Open-market purchases inject reserves into the banking system, increasing the money supply. In the money market, the supply of money shifts right, reducing the nominal interest rate. (b) In the dollar forex market (vertical axis: foreign currency per dollar; horizontal axis: quantity of dollars), lower U.S. interest rates reduce the attractiveness of U.S. financial assets. Foreign investors reduce their demand for dollars (D$ shifts left), and American investors increase capital outflows, supplying more dollars (S$ shifts right). The new equilibrium shows a lower exchange rate—the dollar depreciates. (c) The depreciated dollar makes U.S. exports relatively cheaper for foreign consumers and foreign imports more expensive for American consumers. Therefore, U.S. exports increase, imports decrease, and net exports rise. (d) Because net exports are a component of aggregate demand (AD = C + I + G + NX), the increase in net exports shifts aggregate demand rightward. This reinforces the Fed's original expansionary goal of increasing real GDP and combating the recession. Monetary policy is thus more effective in an open economy than in a closed economy. (e) Under a fixed exchange rate, the Fed would be required to defend the peg. As the lower interest rate puts downward pressure on the dollar, the Fed would need to buy dollars using foreign currency reserves, which contracts the money supply and raises interest rates back up. This process undoes the expansionary policy. The impossible trinity implies that with free capital mobility and a fixed rate, independent monetary policy is not possible.