How Exchange Rates Work and What Moves Currency Values

What Is an Exchange Rate?

An exchange rate is the price of one currency expressed in terms of another. If the USD/EUR exchange rate is 0.92, it means one US dollar can be exchanged for 0.92 euros. Exchange rates are quoted in pairs: the first currency (the base currency) is being bought or sold, and the second (the quote currency) is the pricing unit.

Exchange rates are not set by governments in most developed economies; they emerge from the continuous interaction of buyers and sellers in the foreign exchange (forex) market — the largest and most liquid financial market in the world, with daily trading volumes exceeding $7 trillion. The market operates 24 hours a day, five days a week, across financial centers in London, New York, Tokyo, Singapore, and Sydney.

Types of Exchange Rate Regimes

Countries choose among several exchange rate systems:

• Floating exchange rate — the currency's value is determined entirely by market supply and demand. The US dollar, euro, British pound, and Japanese yen all float. This is the dominant regime among major economies.
• Managed float (dirty float) — the currency floats but the central bank occasionally intervenes to smooth excessive volatility or prevent misalignment. Most large emerging market currencies operate this way.
• Fixed (pegged) exchange rate — the government or central bank ties the currency to another currency or a basket of currencies. The Hong Kong dollar is pegged to the US dollar; Saudi Arabia's riyal is pegged to the dollar at a fixed rate.
• Currency union — multiple countries share a single currency. The eurozone's 20 member states all use the euro and conduct monetary policy through the ECB.

What Drives Exchange Rate Movements

Exchange rates are determined by supply and demand for a currency, which is driven by multiple interacting factors:

Interest Rate Differentials

When a country's interest rates rise relative to other countries, its currency typically appreciates. Higher rates attract foreign investors seeking better returns on bonds and deposits — they must buy the local currency to invest, increasing demand. This is called carry trade when investors borrow in low-rate currencies to invest in high-rate ones.

Inflation Differentials

A country with persistently higher inflation than its trading partners will typically see its currency depreciate over time. Higher inflation erodes the purchasing power of the currency, making its goods more expensive abroad and imports cheaper domestically — reducing demand for the currency. The purchasing power parity (PPP) theory holds that exchange rates should adjust until identical goods cost the same in both countries.

Current Account and Trade Flows

A country's current account balance — the sum of trade in goods, services, income, and transfers — affects currency demand. Countries that export more than they import receive more foreign currency than they pay out; foreigners must buy the local currency to pay for those exports, supporting demand. A persistent trade deficit (more imports than exports) means a country is constantly supplying its own currency to foreigners, creating downward pressure.

Economic Growth and Prospects

Strong economic growth attracts foreign direct investment and portfolio investment, both of which require purchasing the local currency. Positive growth surprises often cause currency appreciation; recessions or poor growth forecasts cause depreciation.

Political Stability and Risk Sentiment

Currencies of stable, predictable political economies command a premium. Political crises, debt defaults, or social instability cause investors to sell a currency and seek safety in more stable alternatives. In times of global stress, investors typically flee to safe-haven currencies: the US dollar, Swiss franc, and Japanese yen tend to appreciate when fear rises globally.

The Role of Central Banks and Government Intervention

Central banks intervene in forex markets to manage excessive currency movements. Japan's central bank has intervened repeatedly to prevent excessive yen strengthening (which hurts exporters) or weakening (which raises import costs). China maintains a managed float, with the PBOC setting a daily midpoint and allowing trading only within a band around it.

The US Treasury periodically labels countries as currency manipulators when they are deemed to be artificially suppressing their currency's value to gain an export advantage. Such designations can trigger trade negotiations or tariffs.

Real vs. Nominal Exchange Rates

The nominal exchange rate is the actual market rate you see quoted. The real exchange rate adjusts the nominal rate for inflation differentials between countries, measuring the actual purchasing power or competitiveness of a currency. If a country's nominal exchange rate holds steady but its inflation runs faster than its trading partners, its real exchange rate appreciates — its goods become less competitive even though the nominal rate has not moved.

The real effective exchange rate (REER) is a trade-weighted average of a currency against a basket of partner currencies, adjusted for inflation. It is a key measure of international competitiveness used by economists and central banks.

Exchange Rates and Trade, Inflation, and Investment

Exchange rate movements ripple through economies in multiple ways:

• Exports and imports: A weaker currency makes a country's exports cheaper for foreigners and imports more expensive domestically, potentially boosting export industries and widening the trade balance over time (the J-curve effect describes the initial deterioration before improvement).
• Inflation: Currency depreciation raises import prices, contributing to inflation. Countries that import significant amounts of food or energy (priced in dollars globally) are especially vulnerable to pass-through inflation.
• Foreign debt burdens: Countries or companies that borrowed in foreign currency face higher repayment costs when their own currency depreciates — a key driver of emerging market debt crises.

Summary

Exchange rates reflect the collective judgment of the global forex market about the relative value of currencies, driven by interest rate differentials, inflation, trade balances, growth prospects, and risk sentiment. No single factor dominates at all times; exchange rate forecasting is notoriously difficult even for professional economists. Understanding the underlying drivers gives businesses, investors, and travelers a framework for interpreting why currencies move and how those movements affect the broader economy.