1. Balance of Payments
When a country trades with the rest of the world, every transaction is recorded in a ledger called the Balance of Payments (BOP). Think of it as a country's financial report card for all international activity.
Balance of Payments (BOP): A record of all economic transactions between the residents of a country and the rest of the world during a given time period. It has two main accounts that must sum to zero.
The Two Accounts
Current Account
Tracks the flow of goods, services, and income.
- Trade Balance (Exports − Imports of goods & services) — the largest component
- Net Income from abroad (wages, investment returns earned overseas)
- Net Transfers (foreign aid, remittances sent to/from other countries)
Current Account Surplus: Country exports more than it imports (net inflow of money for goods).
Current Account Deficit: Country imports more than it exports (net outflow of money for goods). The US has run a current account deficit for decades.
Financial (Capital) Account
Tracks the flow of financial assets — money invested across borders.
- Foreign Direct Investment (FDI) — building a factory abroad
- Portfolio Investment — buying foreign stocks & bonds
- Government Asset Transactions — central banks buying/selling foreign reserves
Capital Account Surplus: More money flowing IN from foreigners investing here.
Capital Account Deficit: More money flowing OUT as domestic residents invest abroad.
The Golden Rule: They Must Balance
If a country runs a current account deficit (imports > exports), it must run a financial account surplus (capital inflow) of the same size — and vice versa. The money flowing out to buy imports comes back in as foreign investment.
🧠 Intuitive Example: The US buys $500B more in foreign goods than it sells (current account deficit of $500B). Where does that $500B go? Foreign countries use it to buy US assets — Treasury bonds, stocks, real estate (financial account surplus of $500B). The books balance.
| Scenario | Current Account | Financial Account |
|---|---|---|
| US imports more than it exports | Deficit (−) | Surplus (+) — foreigners invest here |
| US exports more than it imports | Surplus (+) | Deficit (−) — US invests abroad |
2. Exchange Rates
When countries trade, they use different currencies. An exchange rate is simply the price of one currency expressed in terms of another. Getting the language right is critical for the AP exam.
Exchange Rate: The price of one currency in terms of another. For example, if $1 = ¥150, the exchange rate of the dollar in terms of yen is 150.
Appreciation vs. Depreciation
Appreciation (Currency Gets Stronger)
The currency can buy more foreign currency than before.
Example: $1 used to buy ¥100, now buys ¥150. The dollar appreciated — it's worth more yen.
- US exports become more expensive for foreigners → ↓ Exports
- Imports become cheaper for Americans → ↑ Imports
- Net exports (X − M) decrease
Depreciation (Currency Gets Weaker)
The currency can buy less foreign currency than before.
Example: $1 used to buy ¥150, now buys ¥100. The dollar depreciated — it's worth fewer yen.
- US exports become cheaper for foreigners → ↑ Exports
- Imports become more expensive for Americans → ↓ Imports
- Net exports (X − M) increase
🧠 Memory Trick — "SPICE":
Strong currency = Purchasing power up = Imports Cheap = Exports expensive
Or simply: a strong dollar makes foreign stuff cheap (good for tourists and importers) but makes US stuff expensive abroad (bad for exporters).
Exchange Rate Systems
| System | How It Works | Key Detail |
|---|---|---|
| Floating (Flexible) | Exchange rates are determined by supply and demand in the foreign exchange market. No government intervention. | Most major currencies today (USD, EUR, JPY, GBP). This is the system tested on the AP exam. |
| Fixed (Pegged) | Government sets the exchange rate at a specific value and buys/sells its own currency to maintain that rate. | Requires large foreign currency reserves. Example: China historically pegged the yuan to the dollar. |
| Managed Float | Mostly floating, but the central bank occasionally intervenes to smooth out extreme fluctuations. | Most common in practice. Not heavily tested on AP exam. |
Calculating Exchange Rates
Converting Between Currencies
If $1 = €0.85, then:
To flip an exchange rate, just take the reciprocal. If $1 = ¥150, then ¥1 = $0.00667 (1/150).
Exam Tip: Always check the units. "What is the exchange rate of the dollar in terms of euros?" means: how many euros per dollar? Answer: €0.85 per $1.3. The Foreign Exchange (FOREX) Market
The FOREX market is where currencies are traded. It works exactly like any other market — supply and demand determine the price (exchange rate). This graph appears on every AP Macro exam.
Reading the FOREX Graph
| Component | Explanation |
|---|---|
| Y-axis | The price of the dollar in terms of a foreign currency (e.g., yen per dollar, ¥/$). When this goes up, the dollar has appreciated. |
| Demand for Dollars (D$) | Foreigners who want dollars — to buy US exports, invest in US assets, or travel to the US. Downward sloping: when the dollar is cheaper, foreigners demand more of it. |
| Supply of Dollars (S$) | Americans who are selling dollars — to buy foreign goods (imports), invest abroad, or travel overseas. Upward sloping: when the dollar is worth more foreign currency, Americans supply more dollars (foreign stuff looks cheap). |
What Shifts D$ and S$?
This is the core of Unit 6 FRQs. Every shift traces back to one of these reasons:
| Factor | Effect on Dollar | Mechanism |
|---|---|---|
| ↑ US Interest Rates | $ Appreciates | Higher returns attract foreign investors → they demand more $ to buy US bonds → D$ shifts right → dollar appreciates. |
| ↓ US Interest Rates | $ Depreciates | Lower returns push investors abroad → Americans supply more $ to buy foreign assets → S$ shifts right → dollar depreciates. |
| ↑ US Income / GDP | $ Depreciates | Richer Americans buy more imports → supply more $ to get foreign currencies → S$ shifts right → dollar depreciates. |
| ↑ US Inflation (relative to trading partners) |
$ Depreciates | US goods become relatively expensive → foreigners buy fewer US goods (↓ D$) and Americans buy more imports (↑ S$) → dollar depreciates. |
| ↑ Foreign Demand for US Goods | $ Appreciates | Foreigners need dollars to buy US exports → D$ shifts right → dollar appreciates. |
| Speculation / Confidence | Varies | If investors expect the dollar to strengthen, they buy dollars now → D$ shifts right → self-fulfilling appreciation. |
🎯 The #1 AP Exam Chain (Interest Rates → FOREX):
Fed raises interest rates → foreign investors want higher US returns → they need dollars to invest → D$ shifts right → dollar appreciates → US exports become more expensive, imports become cheaper → Net exports fall → AD shifts left (partially offsetting the initial contractionary policy).
The exam loves asking you to trace this full chain from monetary policy → money market → FOREX → net exports → AD.
Important: Two Currencies, One Market
Every FOREX transaction involves two currencies. When the dollar appreciates, the other currency (yen, euro, etc.) depreciates by the same logic — and vice versa. They are mirror images.
4. Net Exports & Capital Flows
This section ties everything together: how exchange rates, interest rates, fiscal policy, and monetary policy all connect through international trade and investment flows. This is where the AP exam tests your ability to think across multiple graphs simultaneously.
The Fundamental Identity
Or equivalently: Current Account Balance + Financial Account Balance = 0.
If a country runs a trade deficit (net exports are negative), it must receive a net capital inflow (financial account surplus) of the same size. The money leaving for imports comes back as foreign investment.
The Big Picture: How Policy Affects the Open Economy
Here are the two master chains that connect everything in the course. These are FRQ gold:
Chain 1: Expansionary Monetary Policy → Open Economy Effects
Fed buys bonds → ↑ MS → ↓ nominal interest rate
→ ↓ US interest rates relative to world → foreign investors pull money out / Americans invest abroad
→ ↑ Supply of $ in FOREX (or ↓ Demand for $)
→ Dollar depreciates
→ US exports cheaper, imports more expensive → ↑ Net Exports (Xn)
→ AD shifts right (reinforcing the expansionary effect)
→ ↑ Real GDP, ↓ Unemployment, ↑ Price Level
Chain 2: Expansionary Fiscal Policy → Open Economy Effects
Government runs a deficit (↑ G or ↓ T) → ↑ borrowing
→ DLF shifts right → ↑ real interest rate (crowding out)
→ Higher US interest rates attract foreign capital → foreigners demand more $
→ Dollar appreciates
→ US exports more expensive, imports cheaper → ↓ Net Exports (Xn)
→ AD shifts right by even less than crowding out alone would suggest
→ This is called the "twin deficits" — budget deficit causes trade deficit
🎯 The Twin Deficits Hypothesis: Government budget deficit → ↑ interest rates → dollar appreciates → trade deficit widens. A budget deficit and a trade deficit tend to move together. This is one of the most elegant connections on the AP exam.
Summary: Policy → Interest Rate → Exchange Rate → Net Exports
| Policy | Interest Rate | Dollar | Net Exports | Net Effect on AD |
|---|---|---|---|---|
| Expansionary Monetary | ↓ | Depreciates | ↑ Xn | AD↑ reinforced (Xn helps) |
| Contractionary Monetary | ↑ | Appreciates | ↓ Xn | AD↓ reinforced (Xn hurts more) |
| Expansionary Fiscal | ↑ (crowding out) | Appreciates | ↓ Xn | AD↑ weakened (crowding out + Xn) |
| Contractionary Fiscal | ↓ | Depreciates | ↑ Xn | AD↓ weakened (Xn partially offsets) |
Capital Flows and Developing Countries
Capital flows matter enormously for developing economies:
| Concept | Explanation |
|---|---|
| Capital Inflow (Benefits) | Foreign investment brings funds for factories, infrastructure, and technology → promotes growth. Developing nations often rely on foreign capital because domestic saving is low. |
| Capital Inflow (Risks) | "Hot money" can leave suddenly if investors lose confidence → currency collapses, interest rates spike, financial crisis. (Example: Asian Financial Crisis 1997.) |
| Capital Flight | When investors rapidly pull money out of a country due to political instability, high inflation, or loss of confidence → currency depreciates sharply → economic crisis. |
The Complete AP Macro Graph Toolkit
By now, you've mastered every graph the AP exam can throw at you. Here's the full list and when each is used:
| Graph | What It Shows | Y-axis / X-axis |
|---|---|---|
| PPC | Trade-offs, efficiency, growth | Good A / Good B |
| AD-AS | Price level & real GDP determination | PL / Real GDP |
| Money Market | Nominal interest rate (monetary policy) | Nominal i / Q of Money |
| Loanable Funds | Real interest rate (fiscal policy / crowding out) | Real r / Q of LF |
| Phillips Curve | Inflation-unemployment trade-off | Inflation / Unemployment |
| FOREX | Exchange rate determination | Foreign currency per $ / Q of $ |
Unit 6 Key Formulas & Rules
Current Account + Financial Account = 0
$ Appreciates ⟺ Foreign Currency Depreciates
↑ US Interest Rate → $ Appreciates → ↓ Net Exports
↓ US Interest Rate → $ Depreciates → ↑ Net Exports
Budget Deficit → ↑ r → $ Appreciates → Trade Deficit (Twin Deficits)
Monetary policy effects on Xn reinforce. Fiscal policy effects on Xn offset.
🎉 You've Completed All 6 Units!
You now have the complete framework for AP Macroeconomics. Every question on the exam — MCQ or FRQ — connects back to the concepts, graphs, and chains in these six units. Review, practice, and go get that 5.
End of Unit 6 Study Guide. End of AP Macroeconomics Course.