# Changes in Exchange Rates and Net Exports

> AP Macroeconomics · Unit 6: Open Economy: International Trade and Finance
> Source: https://www.owlsprep.com/study/ap-macroeconomics-u6-changes-in-exchange-rates-and/

This sub-topic explains how changes in currency values impact net exports and aggregate demand in open economies, and how exogenous net export changes alter equilibrium exchange rates. It is heavily tested on both AP Macroeconomics sections.

**Prerequisites:** Interpreting the foreign exchange market model; Net exports definition and aggregate demand components; Nominal vs. real exchange rate concepts

## Learning objectives

- Explain how exchange rate changes affect export/import prices and net exports
- Analyze reverse causality between net export changes and equilibrium exchange rates
- Connect exchange rate changes to aggregate demand shifts and domestic outcomes
- Avoid common exam pitfalls in open economy relationship analysis

## Core Relationship: Exchange Rate Changes to Net Exports

This topic explores how changes in a currency's value alter the prices of exports and imports, changing net exports, a core component of aggregate demand. AP Macroeconomics follows the standard convention where the nominal exchange rate $e$ is defined as the number of units of foreign currency you can buy with one unit of domestic currency.

**Nominal Exchange Rate (AP Convention)** — Number of units of foreign currency that can be exchanged for 1 unit of domestic currency. A rising $e$ means domestic currency appreciates; a falling $e$ means domestic currency depreciates.

*Notation:* $e$

To see how this works: the foreign currency price of a domestic export equals the domestic price multiplied by $e$. If $e$ rises (appreciation), the foreign price of domestic exports rises, so foreigners buy fewer exports. For domestic buyers of imports, the domestic price of a foreign good equals the foreign price divided by $e$, so appreciation makes imports cheaper for domestic consumers, who buy more imports.

- Domestic currency appreciation ($\uparrow e$): Exports $\downarrow$, Imports $\uparrow$, Net Exports $NX \downarrow$
- Domestic currency depreciation ($\downarrow e$): Exports $\uparrow$, Imports $\downarrow$, Net Exports $NX \uparrow$

**Worked example:** A Canadian wine bottle costs 20 CAD. The U.S. is the domestic economy, with an initial exchange rate of 1 USD = 1.33 CAD. If the USD appreciates so that 1 USD = 1.5 CAD, what happens to the USD price of the wine for U.S. consumers, and how does this change U.S. net exports, ceteris paribus?

1. Calculate the initial USD price:

   $$P_{USD} = \frac{20}{1.33} \approx 15$$
2. Calculate the new USD price after appreciation:

   $$P_{new} = \frac{20}{1.5} \approx 13.33$$
3. The lower USD price means U.S. consumers will buy more Canadian wine, so U.S. imports from Canada increase.
4. Since $NX = X - M$, higher $M$ means U.S. net exports decrease, ceteris paribus.

> **Exam tip:** Always confirm the exchange rate convention before solving: if a question defines $e$ as domestic currency per foreign currency, reverse the relationship above. AP problems almost always use foreign currency per domestic currency, but double-check to avoid reversed logic.

## Reverse Causality: Net Export Changes to Exchange Rates

AP exams regularly test the reverse direction of causality: exogenous changes in net exports (changes unrelated to exchange rates) shift supply or demand for currency in the foreign exchange market, changing the equilibrium exchange rate. Recall that demand for domestic currency comes from foreigners wanting to buy domestic exports or assets, while supply of domestic currency comes from domestic consumers wanting to buy foreign imports or assets.

If foreign demand for domestic exports increases exogenously, foreigners need more domestic currency to purchase these goods, shifting demand for domestic currency right, increasing equilibrium $e$, leading to domestic currency appreciation. Conversely, if domestic demand for foreign imports increases exogenously, domestic consumers supply more domestic currency to get foreign currency, shifting supply right, decreasing equilibrium $e$, leading to domestic currency depreciation.

**Worked example:** Exogenous change: Chinese consumers increase their demand for Australian beef, ceteris paribus, with the Australian dollar (AUD) as the domestic currency. How does this change affect the equilibrium exchange rate for AUD, and will AUD appreciate or depreciate?

1. Higher Chinese demand for Australian exports means Chinese buyers need more AUD to purchase the beef, so demand for AUD in the forex market increases.
2. The original equilibrium is the intersection of initial demand $D_1$ and supply $S$ for AUD. Demand shifts right from $D_1$ to $D_2$.
3. The new intersection of $D_2$ and $S$ occurs at a higher value of $e$, where $e$ is Chinese yuan (CNY) per AUD.
4. A higher $e$ means 1 AUD buys more CNY than before, so the Australian dollar appreciates, ceteris paribus.

> **Exam tip:** When shifting forex curves, always ask: who wants what currency? If foreigners want more domestic goods, they demand domestic currency, not supply it. This is the most common mistake in reverse causality questions.

## Connecting Exchange Rates to Aggregate Demand

Net exports are one of the four core components of aggregate demand, so any change in net exports from exchange rate changes shifts the entire aggregate demand curve, impacting domestic real GDP and the price level:

$$AD = C + I + G + NX$$

The full causal chain for depreciation is: Domestic currency depreciation $\rightarrow \downarrow e \rightarrow$ export prices fall for foreigners $\rightarrow$ exports rise $\rightarrow$ import prices rise for domestic consumers $\rightarrow$ imports fall $\rightarrow \uparrow NX \rightarrow$ AD shifts right. A rightward AD shift increases short-run real GDP and the aggregate price level, ceteris paribus. For appreciation, the chain reverses.

**Worked example:** The European Central Bank undertakes expansionary monetary policy, which lowers the euro (EUR) interest rate ceteris paribus. Lower interest rates cause the EUR to depreciate relative to all other currencies. Starting from long-run equilibrium, how does this depreciation affect the euro area AD curve, real GDP, and the price level in the short run?

1. EUR depreciation means 1 EUR buys less foreign currency, so European exports are cheaper for foreign buyers, and imports into Europe are more expensive for European consumers.
2. Exports increase, imports decrease, so $NX = X - M$ increases.
3. Since NX is a component of AD, an increase in NX shifts the entire AD curve right from $AD_1$ to $AD_2$.
4. The new short-run equilibrium (intersection with the SRAS curve) occurs at a higher level of real GDP and a higher aggregate price level than the original long-run equilibrium.

> **Exam tip:** When asked to connect exchange rate changes to AD on an FRQ, never skip the intermediate net exports step. AP FRQ rubrics require the explicit chain from exchange rate $\rightarrow$ NX $\rightarrow$ AD shift to award full credit.

## AP Style Concept Check

**Check your understanding**

Test your understanding of core concepts:

1. If the Japanese yen depreciates relative to the US dollar, ceteris paribus, which of the following correctly describes the effect on Japan’s net exports with the US?

   - Net exports increase, because Japanese exports to the US are more expensive and US imports into Japan are cheaper.
   - Net exports increase, because Japanese exports to the US are cheaper and US imports into Japan are more expensive.
   - Net exports decrease, because Japanese exports to the US are more expensive and US imports into Japan are cheaper.
   - Net exports decrease, because Japanese exports to the US are cheaper and US imports into Japan are more expensive.

   *Answer:* Net exports increase, because Japanese exports to the US are cheaper and US imports into Japan are more expensive.

   *Why:* Correct: Depreciation of the yen makes Japanese exports cheaper for US consumers and US imports more expensive for Japanese consumers, increasing net exports.

## Common pitfalls

- **Wrong:** Assuming that when domestic currency appreciates, both exports and imports decrease, so net exports do not change
  - Why it fails: Students confuse quantity effects for exports vs. imports; appreciation reduces export quantities but increases import quantities, not both
  - Correct: Always separate the effects: appreciation → X↓, M↑ → NX↓; depreciation → X↑, M↓ → NX↑
- **Wrong:** Shifting supply of domestic currency when foreign demand for domestic exports increases
  - Why it fails: Students mix up who supplies and demands currency in the forex market
  - Correct: Whenever exogenous foreign demand for domestic goods increases, foreigners need more domestic currency, so demand for domestic currency shifts right, not supply
- **Wrong:** Claiming that an exogenous increase in net exports causes domestic currency depreciation
  - Why it fails: Students memorize 'depreciation increases NX' and reverse the causal direction incorrectly
  - Correct: If NX increases from higher foreign demand for domestic goods, demand for domestic currency rises, leading to appreciation, not depreciation
- **Wrong:** Reversing the effect of appreciation on net exports, i.e., stating appreciation increases NX
  - Why it fails: Students mix up exchange rate conventions, leading to flipped logic
  - Correct: Write the causal chain on scratch paper before answering to confirm: 'appreciation = domestic goods more expensive for foreigners → exports fall → NX falls'
- **Wrong:** Skipping the net exports step when connecting exchange rate changes to AD shifts on FRQs
  - Why it fails: Students assume the connection is obvious and do not state the intermediate step
  - Correct: Always explicitly write that exchange rate changes alter NX before stating the effect on AD, to meet rubric requirements

## Cheatsheet

| Category | Formula / Rule | Notes |
| --- | --- | --- |
| Net Exports Definition | $NX = X - M$ | $X =$ Exports, $M =$ Imports; can be positive (surplus) or negative (deficit) |
| AP Exchange Rate Convention | $e =$ Foreign Currency per 1 Unit of Domestic Currency | If reversed in a question, reverse all rules below |
| Effect of Domestic Appreciation | $\uparrow e \rightarrow \downarrow X, \uparrow M \rightarrow \downarrow NX$ | Ceteris paribus (constant price levels) |
| Effect of Domestic Depreciation | $\downarrow e \rightarrow \uparrow X, \downarrow M \rightarrow \uparrow NX$ | Ceteris paribus applies |
| Exogenous ↑ Foreign Demand for Domestic Exports | $\uparrow X \rightarrow \uparrow$ Demand for Domestic Currency $\rightarrow \uparrow e \rightarrow$ Appreciation | Reverse causality rule: NX change causes exchange rate change |
| Exogenous ↑ Domestic Demand for Foreign Imports | $\uparrow M \rightarrow \uparrow$ Supply of Domestic Currency $\rightarrow \downarrow e \rightarrow$ Depreciation | Works for any exogenous import demand change |

## What's next

The relationship between exchange rates and net exports is the foundation for all open-economy macroeconomic policy analysis in AP Macroeconomics Unit 6. Understanding this connection allows you to analyze how fiscal and monetary policy work differently in open economies compared to closed economies, a high-weight topic frequently tested on full-point FRQ questions. You will extend this relationship to analyze capital flows, policy crowding out, and the impacts of currency intervention on domestic and foreign macroeconomic outcomes.

- [Unit 6 Open Economy Overview](https://www.owlsprep.com/study/ap-macroeconomics-u6-overview/)

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