Chapter 33: Foreign Exchange and Foreign Trade

Book: Economics 101

Author: Alfred Mill & Michele Cagan

Type: Chapter

Category: Economics

Difficulty: Beginner

Reading time: 10 min

Core idea

An exchange rate is the price of one currency expressed in another. The foreign exchange (FX) market — annual volume north of $2 quadrillion, running 24 hours a day — is where those prices are continuously discovered. Three forces dominate exchange-rate movement: relative interest rates (capital flows toward higher real yields), relative inflation (capital flees less-stable currencies), and relative economic growth (rising incomes increase imports, supplying more of the home currency to FX markets, which counterintuitively weakens it).

Every cross-border transaction is also a recordkeeping event. The balance of payments tracks all inflows and outflows: net exports plus factor income and transfers make up the current account; net foreign investment plus official central-bank reserves make up the financial account. The two account balances always sum to zero by construction — money in must equal money out, even if the categories shift dramatically year to year.

Why it matters

Exchange rates touch everything you buy

The price of imported coffee, foreign cars, smartphones, semiconductors, and overseas vacations is set in part by the exchange rate. When the dollar strengthens, imports get cheaper for Americans and US exports get more expensive abroad. When it weakens, the opposite — and US manufacturers tend to celebrate quietly. Inflation in any open economy is partially imported, and the FX rate is the conveyor belt.

The dollar is the world’s reserve currency

Most central banks hold the majority of their foreign reserves in US dollars. That gives the US enormous advantages — it borrows cheaply from the world, prints the asset that everyone wants to hold, and rarely worries about a currency run. It also creates a tail risk that nothing else has: if major holders (China holds over $3 trillion of dollar assets; Japan over $1 trillion) chose to diversify away, the dollar would weaken sharply and US borrowing costs would jump. Reserve-currency status is a privilege, not a permanent fact.

Three regimes, three trade-offs

A country can let its currency float (US, UK, Japan), peg it to another currency (Hong Kong pegs to the dollar), or share a currency in a monetary union (the euro). Each regime trades off monetary independence, exchange-rate stability, and capital mobility — you can have any two, not all three. Knowing which two a country has chosen explains most of its macroeconomic constraints.

Key takeaways

Key takeaways

• An exchange rate is the price of one currency in terms of another, set continuously in the world's largest market — over $2 quadrillion in annual volume.
• The dollar dominates: it is on one side of the vast majority of FX trades, and most countries hold dollars as their primary reserve.
• When real interest rates rise in country A relative to country B, capital flows toward A — A's currency appreciates, B's depreciates. This tendency is called interest rate parity.
• High inflation drives a currency lower; people seek more stable currencies as a store of value.
• Counterintuitively, faster economic growth tends to weaken a currency, because higher incomes increase imports and supply more of the home currency abroad.
• The balance of trade is exports minus imports. The US runs a deficit in goods and a surplus in services — together still a net deficit.
• Exchange-rate regimes come in three flavors: floating (market-determined), pegged (central bank defends a rate), and unified (single currency across multiple countries, like the euro).

Mental model — what moves an exchange rate

click to zoom

Three macro drivers and one policy lever determine where the exchange rate settles.

Read it as: Four levers move a currency. Three are economic conditions (interest, inflation, growth) and one is direct intervention by a central bank. The “rising income weakens the currency” channel is the counterintuitive one — a richer country imports more, supplying more of its own currency to FX markets, which lowers its price.

Mental model — a cross-border purchase, end to end

click to zoom

What actually happens when a US buyer pays a Japanese supplier.

Read it as: Every cross-border purchase has three layers — the underlying trade, the bank-to-bank transfer, and the FX conversion. Each transaction adds a tiny shove on the exchange rate: in this case, slightly more USD supplied to the FX market, slightly more JPY demanded. Multiply by billions a day and you get the macro pattern.

The three exchange-rate regimes

Regime	Examples	Pros	Cons
Floating	US, UK, Japan, Australia	Monetary policy is free to fight domestic recessions or inflation	Exporters face FX risk; currency can swing on speculation
Pegged to another currency	Hong Kong (to USD), Denmark (to EUR), Saudi Arabia (to USD)	FX stability; predictable trade pricing	Must spend reserves defending the peg; gives up monetary independence
Unified currency	Eurozone (19 countries share the euro)	Frictionless trade within the bloc; deep capital markets	No country can devalue to escape a slump; need fiscal coordination

Practical application

Tracing a Fed rate hike to global markets

1. Fed raises the federal funds rate. US short-term rates rise relative to other major economies.

2. Global capital rotates. Investors holding euros, yen, or pesos sell those currencies to buy dollar-denominated bonds at the new higher yield.

3. Dollar appreciates. The increased demand for dollars pushes the USD up against most currencies.

4. Emerging-market squeeze. Countries with dollar-denominated debt now owe more in their local currency. Borrowing costs rise. Capital outflows accelerate.

5. US trade deficit widens. US imports get cheaper; US exports get more expensive. Net exports fall, partially offsetting the domestic effect the Fed was hoping for.

6. Eventually: interest rate parity. The appreciated dollar is now expected to depreciate over time. That expected depreciation eats into the yield advantage, and capital flows normalize. The currency may even overshoot before settling.

Reading a balance-of-trade headline

A trade deficit is not necessarily bad

A trade deficit means a country is consuming more goods and services than it produces — the rest of the world is, in effect, lending it the difference. For the US, this is sustainable largely because the dollar is the global reserve currency: foreigners are happy to hold dollar assets, so the “borrowing” is willingly funded. For a small economy without that privilege, a persistent trade deficit can foreshadow a currency crisis. Context matters more than the headline.

Example: A Swiss watchmaker watches the dollar

Imagine “Helvetia Horlogerie,” a Swiss watch company with most of its sales in the United States. It prices each watch at $5,000 retail. Its costs (Swiss labor, materials) are denominated in Swiss francs.

Scenario A: 1 USD = 0.95 CHF. A $5,000 sale converts to CHF 4,750. Helvetia’s costs are CHF 3,500 per watch, leaving CHF 1,250 in profit per unit.

Scenario B: The dollar weakens to 1 USD = 0.80 CHF (perhaps the Fed has been cutting rates while the Swiss National Bank holds steady). Now a $5,000 sale converts to only CHF 4,000. Costs are still CHF 3,500. Profit collapses to CHF 500 per watch — a 60% drop in profitability, with no change in product, pricing, or unit sales.

Helvetia’s options: raise US prices (risking lost sales), hedge with FX forwards (paying for predictability), shift some production to a dollar-denominated location, or accept lower profits. Notice that none of these options involves making better watches. A change in the exchange rate — a number Helvetia does not control and may not have predicted — has just turned a comfortable business into a marginal one. This is why every multinational has a treasury team obsessing over the FX board.

Caveats

Caution

Exchange-rate models predict direction better than magnitude, and they only work over long horizons. In the short run, FX markets are dominated by trader expectations, geopolitical headlines, central-bank surprise actions, and risk-off flight to safety (which usually means into the dollar even when US fundamentals are deteriorating). A model that says “the dollar should fall over five years” can be exactly right and still see the dollar rally for the first eighteen months. Don’t bet your business on a clean prediction.

Related lessons

Related

Chapter 32: The Stock Market How equity markets respond to dollar moves — especially for multinationals with overseas revenue. Chapter 34: Cryptocurrency A new asset class that sometimes behaves like a currency and sometimes like a speculative security — outside the FX system entirely. Concept: Monetary policy Central-bank actions that shape interest rates and, downstream, exchange rates. Concept: Inflation The other major macro variable that determines whether a currency holds its value.