An exchange rate is the price of one currency in terms of another — how many euros a dollar buys, how many yen, how many pesos. Exchange rates fluctuate constantly, and the movements drive who wins and loses in international trade, how much foreign travel costs, and how American companies’ overseas earnings translate back into dollars. The mechanics are simple; the forces driving the rates are not.
What an Exchange Rate Is
An exchange rate is the conversion price between two currencies. If the EUR/USD rate is 1.08, it means one euro buys $1.08, or equivalently, one dollar buys about €0.93. Quote conventions vary: some currency pairs are quoted with the U.S. dollar as the base (USD/JPY at 150 means $1 buys 150 yen); others quote the other currency first (EUR/USD at 1.08 means €1 buys $1.08). The conventions are largely historical and don’t affect the economics.
Floating vs. Fixed Rates
- Floating rates — Most major currencies (the U.S. dollar, euro, British pound, Japanese yen, Canadian dollar, Swiss franc) trade in open markets where supply and demand set the rate. Governments and central banks may intervene to influence the rate, but they don’t commit to a specific level
- Fixed (pegged) rates — Some countries peg their currency to another (often the U.S. dollar) at a fixed rate. The central bank commits to buying or selling its currency at the peg whenever the market price diverges. Examples include the Hong Kong dollar (pegged to USD) and several Persian Gulf currencies. Maintaining a peg requires substantial foreign currency reserves and gives up monetary policy independence
- Managed float — A middle ground. The currency trades in markets, but the central bank intervenes to keep it within a desired range. China’s renminbi is often described as a managed float
What Moves Exchange Rates
- Interest rate differentials — If U.S. interest rates rise relative to other countries, foreign investors move money to U.S. dollar assets to capture higher yields. That demand for dollars raises the dollar’s exchange rate. The dollar surged in 2022–2023 partly because the Fed raised rates faster than most other central banks
- Inflation differentials — A currency losing purchasing power to inflation tends to depreciate relative to one with lower inflation. Over the long run, purchasing power parity (PPP) suggests exchange rates adjust toward equalizing the price of similar goods across countries — though deviations from PPP can persist for years
- Trade flows — A country exporting more than it imports has foreign buyers seeking its currency to pay for those exports. A country importing more has citizens selling its currency to buy foreign goods. Persistent trade deficits typically pressure a currency downward, though capital inflows can offset
- Capital flows — Foreign direct investment, portfolio investment, and demand for U.S. Treasuries all bring capital into the dollar, increasing its value. Outflows do the reverse
- Political and economic stability — Currencies of stable, well-governed economies tend to attract capital, supporting their value. Currencies of countries with political instability or fiscal stress tend to depreciate
- Central bank intervention — Central banks can buy or sell their own currency to influence the exchange rate. Effectiveness depends on the size of intervention relative to the market and whether it’s consistent with underlying forces
Strong Dollar vs. Weak Dollar — Who Wins, Who Loses
A “strong” or “weak” dollar isn’t inherently good or bad — it creates winners and losers within the U.S. economy:
- Strong dollar benefits — American consumers buying imported goods (electronics, clothing, oil), American tourists traveling abroad (your dollars buy more), American companies importing inputs, the Fed’s fight against inflation (cheaper imports hold down U.S. prices)
- Strong dollar costs — American exporters (their goods become more expensive for foreign buyers), U.S. multinational companies’ overseas earnings (worth less when converted back to dollars), foreign tourists visiting the U.S. (their currency buys less), American manufacturing competing with imports
- Weak dollar reverses everything — Exporters and manufacturers benefit; importers and travelers pay more
The Dollar’s Reserve Currency Role
The U.S. dollar serves as the world’s primary reserve currency. Roughly 58% of global central bank foreign exchange reserves are held in dollars (the second-largest, the euro, is around 20%). The dollar is also the dominant currency for international trade invoicing, oil pricing, and cross-border lending.
This status gives the U.S. an “exorbitant privilege” — persistent global demand for dollars allows the U.S. to borrow cheaply and run persistent trade deficits without facing the currency crises that affect emerging markets. It also makes U.S. sanctions extraordinarily powerful, since blocking access to dollar payments cuts off a country from much of global finance. Whether the dollar’s reserve status will erode in the long run is a recurring debate, but no other currency currently has the combination of liquidity, stability, and acceptance to displace it.
The Bottom Line
Exchange rates are the prices of currencies relative to each other, driven by interest rate differentials, inflation, trade flows, capital movements, and political stability. Most major currencies float in open markets; some are pegged or managed. A strong dollar makes imports cheaper and exports harder, with the reverse for a weak dollar. The U.S. dollar’s role as the global reserve currency gives the U.S. unusual financial flexibility and gives dollar movements outsized importance worldwide.