U6.3 The Foreign Exchange Market
Master the AP Macro FX market diagram: draw demand and supply for a currency, find sources of each curve, and predict equilibrium exchange-rate effects.
What you'll do in this lesson
A voice-first session with the Crimsora tutor on U6.3 The Foreign Exchange Market, then targeted practice and FRQs — with the tutor adapting to where you get stuck.
What this lesson covers
Every time you buy a Japanese game, a European vacation, or a share of a foreign company, you enter the foreign exchange (FX) market. In topic 6.3 you learn to model that market with a supply-and-demand diagram for a single currency, where the "price" is the exchange rate. This is one of the most reliably tested diagrams in Unit 6, and the good news is that it behaves exactly like the supply-and-demand graphs you already know — you just have to be careful about what is on each axis and who is buying and selling. Master the mechanics here, and topics 6.4 and 6.5 (determinants and effects) become plug-and-play.
Setting Up the FX Diagram
The FX market for a currency puts the exchange rate on the vertical axis and the quantity of that currency on the horizontal axis. Always label the diagram for one specific currency — for example, "Market for the U.S. dollar." The vertical axis then reads as the price of a dollar measured in another currency, such as euros per dollar.
The key habit that prevents most exam errors: title your graph and axes explicitly. If the axis says "euros per dollar," then a movement up the axis means the dollar is appreciating (each dollar buys more euros) and the euro is depreciating.
Because every currency market has a mirror image, appreciation of one currency is always depreciation of the other. On the exam you may be asked to analyze the same event in the market for the dollar and in the market for the euro; the two diagrams move in opposite directions.
The key habit that prevents most exam errors: title your graph and axes explicitly. If the axis says "euros per dollar," then a movement up the axis means the dollar is appreciating (each dollar buys more euros) and the euro is depreciating.
| Element | What it is |
|---|---|
| Vertical axis | Exchange rate (price of the currency in foreign-currency units) |
| Horizontal axis | Quantity of the currency |
| Demand curve | Downward sloping |
| Supply curve | Upward sloping |
| Equilibrium | Where , giving the market exchange rate |
Why Demand Slopes Down and Supply Slopes Up
Demand for a currency comes from foreigners who need it to buy that country's goods, services, and assets. Demand for the U.S. dollar arises when foreigners want U.S. exports, want to invest in U.S. financial assets, or want to travel to the United States. The curve slopes downward because as the dollar depreciates (becomes cheaper in foreign currency), U.S. goods and assets become cheaper to foreigners, so they demand a larger quantity of dollars.
Supply of a currency comes from that country's own residents who must give up their currency to obtain foreign currency. Americans supply dollars when they import foreign goods, invest abroad, or travel overseas. The curve slopes upward because as the dollar appreciates (becomes more valuable), foreign goods become cheaper for Americans, so they want more foreign currency and therefore supply more dollars.
A common misconception is thinking the same group both supplies and demands. In these models, foreigners generate demand for the home currency, while home residents generate supply. Anchoring who acts on each side makes it far easier to shift the correct curve when a scenario is given.
Supply of a currency comes from that country's own residents who must give up their currency to obtain foreign currency. Americans supply dollars when they import foreign goods, invest abroad, or travel overseas. The curve slopes upward because as the dollar appreciates (becomes more valuable), foreign goods become cheaper for Americans, so they want more foreign currency and therefore supply more dollars.
A common misconception is thinking the same group both supplies and demands. In these models, foreigners generate demand for the home currency, while home residents generate supply. Anchoring who acts on each side makes it far easier to shift the correct curve when a scenario is given.
Shifting the Curves and Reading Equilibrium
To predict the new exchange rate, decide which curve shifts and in which direction, then read the new equilibrium. The determinants themselves are detailed in 6.4, but the mechanics are pure supply and demand.
An increase in demand for the dollar (rightward shift) raises the equilibrium exchange rate — the dollar appreciates. A decrease in demand lowers it — the dollar depreciates. On the supply side, an increase in the supply of dollars (rightward shift) lowers the exchange rate — the dollar depreciates — while a decrease raises it.
Work one curve at a time. If a scenario clearly names foreigners acting, shift demand; if it names home residents acting, shift supply. Then compare the old and new equilibrium exchange rates to state appreciation or depreciation.
An increase in demand for the dollar (rightward shift) raises the equilibrium exchange rate — the dollar appreciates. A decrease in demand lowers it — the dollar depreciates. On the supply side, an increase in the supply of dollars (rightward shift) lowers the exchange rate — the dollar depreciates — while a decrease raises it.
| Change | Curve | Effect on exchange rate | Currency |
|---|---|---|---|
| Foreigners buy more U.S. exports | Demand right | Rises | Appreciates |
| Foreigners buy fewer U.S. assets | Demand left | Falls | Depreciates |
| Americans import more | Supply right | Falls | Depreciates |
| Americans invest abroad less | Supply left | Rises | Appreciates |
How the Exam Tests This Topic
Free-response prompts frequently ask you to "draw a correctly labeled graph of the foreign exchange market for the [currency]" and then "show the effect" of an event. Full credit requires a titled graph, correctly labeled axes with the exchange rate as a foreign-currency price, downward demand, upward supply, an original equilibrium, and a clearly shifted curve with a new equilibrium and arrow.
Multiple-choice questions test the direction of the shift and whether the currency appreciates or depreciates, often pairing the home and foreign currency. Watch for the mirror-image trap: if the dollar appreciates against the euro, the euro depreciates against the dollar.
Two frequent point-losers: shifting the wrong curve because you misidentified who is transacting, and mislabeling the vertical axis so that up means the wrong direction. Always write the axis as a specific ratio (for example, "pesos per dollar") so your appreciation/depreciation conclusion is unambiguous. Finally, remember that the exchange rate is a price, not a quantity — a shift changes the equilibrium rate, and you describe that change as appreciation or depreciation of the currency named in the title.
Multiple-choice questions test the direction of the shift and whether the currency appreciates or depreciates, often pairing the home and foreign currency. Watch for the mirror-image trap: if the dollar appreciates against the euro, the euro depreciates against the dollar.
Two frequent point-losers: shifting the wrong curve because you misidentified who is transacting, and mislabeling the vertical axis so that up means the wrong direction. Always write the axis as a specific ratio (for example, "pesos per dollar") so your appreciation/depreciation conclusion is unambiguous. Finally, remember that the exchange rate is a price, not a quantity — a shift changes the equilibrium rate, and you describe that change as appreciation or depreciation of the currency named in the title.
Key terms
- Exchange rate.
- The price of one currency expressed in units of another currency; the vertical-axis variable in the FX diagram.
- Appreciation.
- An increase in a currency's value, so each unit buys more foreign currency; shown as a higher equilibrium on that currency's graph.
- Depreciation.
- A decrease in a currency's value, so each unit buys less foreign currency; shown as a lower equilibrium on that currency's graph.
- Demand for a currency.
- The desire of foreigners to obtain the currency to buy the country's exports and assets; slopes downward.
- Supply of a currency.
- The amount of the currency residents give up to buy foreign goods and assets; slopes upward.
- Equilibrium exchange rate.
- The rate where quantity of currency demanded equals quantity supplied, clearing the FX market.
- Mirror-image markets.
- The principle that appreciation of one currency is simultaneously depreciation of the other in the paired market.
Worked example
European tourists suddenly increase their travel to the United States. Using a correctly labeled FX market for the U.S. dollar (euros per dollar on the vertical axis), show and explain the effect on the equilibrium exchange rate and state what happens to the dollar and the euro.
Step 1: Set up the graph. Title it "Market for the U.S. dollar." Vertical axis is the exchange rate in euros per dollar; horizontal axis is the quantity of dollars. Draw downward-sloping demand and upward-sloping supply crossing at exchange rate .
Step 2: Identify who is acting. European tourists are foreigners. To pay for U.S. hotels, food, and attractions they must obtain dollars, so this is a change in the demand for dollars, not supply.
Step 3: Determine the direction. More European travel to the U.S. means foreigners want more dollars, so demand shifts right from to .
Step 4: Read the new equilibrium. The intersection moves up along to a higher exchange rate , where . Each dollar now buys more euros.
Step 5: State the conclusion. Because euros per dollar rose, the U.S. dollar appreciates. In the mirror-image market for the euro, the euro depreciates.
Step 2: Identify who is acting. European tourists are foreigners. To pay for U.S. hotels, food, and attractions they must obtain dollars, so this is a change in the demand for dollars, not supply.
Step 3: Determine the direction. More European travel to the U.S. means foreigners want more dollars, so demand shifts right from to .
Step 4: Read the new equilibrium. The intersection moves up along to a higher exchange rate , where . Each dollar now buys more euros.
Step 5: State the conclusion. Because euros per dollar rose, the U.S. dollar appreciates. In the mirror-image market for the euro, the euro depreciates.
Practice questions
On a foreign exchange graph for the Mexican peso with U.S. dollars per peso on the vertical axis, U.S. residents sharply increase purchases of Mexican goods. What happens to the equilibrium exchange rate of the peso?
- Demand for pesos increases, and the peso appreciates
- Supply of pesos increases, and the peso depreciates
- Demand for pesos decreases, and the peso depreciates
- Supply of pesos decreases, and the peso appreciates
Answer: Demand for pesos increases, and the peso appreciates
U.S. residents buying Mexican goods must obtain pesos, which increases the demand for pesos (they supply dollars to get them). The peso's demand curve shifts right, raising the equilibrium dollars-per-peso rate, so the peso appreciates. It is tempting to say supply shifts, but the action of foreigners wanting a currency always shows up as a demand shift in that currency's market.
Suppose Americans dramatically increase their investment in foreign financial assets. Draw a correctly labeled FX market for the U.S. dollar and explain the effect on the equilibrium exchange rate and on the value of the dollar.
Answer: The supply of dollars increases, the equilibrium exchange rate falls, and the dollar depreciates.
To invest abroad, Americans must sell dollars to acquire foreign currency, so they supply more dollars. On the dollar's diagram the supply curve shifts right from to , moving equilibrium down along the demand curve to a lower exchange rate. Since each dollar now buys less foreign currency, the dollar depreciates. The key is recognizing that home residents acting abroad shift supply, not demand.
If the British pound appreciates against the U.S. dollar, which statement must also be true?
- The dollar appreciates against the pound
- The dollar depreciates against the pound
- The quantity of pounds supplied fell to zero
- Both currencies gained value simultaneously
Answer: The dollar depreciates against the pound
FX markets are mirror images: if the pound rises in value relative to the dollar, then the dollar must fall in value relative to the pound. Both currencies cannot appreciate against each other at the same time, and appreciation says nothing about supply falling to zero.
FAQ
- What goes on each axis of the foreign exchange market graph?
- Put the exchange rate on the vertical axis, expressed as the price of the currency in the graph's title measured in foreign-currency units (for example, euros per dollar in the market for dollars). Put the quantity of that currency on the horizontal axis. Labeling the axis as a specific ratio keeps appreciation and depreciation directions clear.
- Who supplies and who demands a currency in this model?
- Foreigners demand the home currency because they need it to buy the country's exports and assets, giving a downward-sloping demand curve. Home residents supply the currency when they sell it to obtain foreign currency for imports and foreign investment, giving an upward-sloping supply curve.
- How do I know whether to shift demand or supply?
- Identify who is transacting. If foreigners want the home currency, shift the demand curve. If home residents are giving up the home currency to get foreign currency, shift the supply curve. Then move it right or left based on whether the desired amount rises or falls.
- Why does appreciation of one currency mean depreciation of another?
- Because an exchange rate is a relative price between two currencies. If one dollar buys more euros, then one euro necessarily buys fewer dollars. Every FX market has a mirror-image market, so gains for one currency are automatically losses for the paired currency.
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