How Exchange Rates Are Determined in Global Currency Markets

$7.5 Trillion Traded Every Day—The Market That Never Sleeps

The foreign exchange market processes approximately $7.5 trillion in daily transactions according to the Bank for International Settlements' 2022 triennial survey. That volume dwarfs every stock exchange on Earth combined. The market operates 24 hours a day, five days a week, as trading desks in Sydney, Tokyo, London, and New York hand off to one another across time zones. No central exchange exists. Currencies trade over-the-counter between banks, corporations, hedge funds, central banks, and retail traders. The exchange rate between any two currencies is simply the price at which buyers and sellers agree to trade—but the forces driving that price are some of the most complex in economics.

Floating vs. Fixed Exchange Rate Regimes

Countries choose how their currency's value relates to others. The choice has profound economic consequences.

Most major economies float their currencies. China operates a managed float, with the People's Bank of China setting a daily reference rate for the yuan and allowing fluctuations within a 2% band. The tension between market forces and government control plays out daily in Beijing.

What Drives Exchange Rate Movements

Six primary forces push currencies up and down. They interact simultaneously, making precise prediction nearly impossible.

• Interest rate differentials: Higher rates attract foreign capital seeking better returns, increasing demand for the currency
• Inflation differentials: Countries with lower inflation see their currency appreciate over time relative to higher-inflation peers
• Trade balances: Countries that export more than they import create demand for their currency as foreign buyers pay for goods
• Government debt levels: High debt raises default concerns, weakening the currency
• Political stability: Uncertainty drives capital to safer currencies (flight to quality)
• Speculation: Traders betting on future movements can amplify or dampen fundamental trends

The carry trade illustrates how interest rates move currencies. A trader borrows Japanese yen at 0.25% interest, converts to Mexican pesos, and invests at 11% interest. The 10.75% spread generates profit—as long as the peso doesn't depreciate against the yen by more than 10.75%. When conditions reverse and traders unwind carry positions simultaneously, the borrowed currency spikes and the invested currency crashes.

Purchasing Power Parity

PPP theory holds that exchange rates should adjust so that identical goods cost the same in different countries. If a basket of goods costs $100 in the U.S. and ¥15,000 in Japan, the PPP exchange rate is 150 yen per dollar.

The Economist's Big Mac Index, published since 1986, compares the price of a Big Mac in different countries to estimate currency over- or undervaluation. In January 2024, a Big Mac cost $5.69 in the U.S. and 24 Swiss francs ($27.19) in Switzerland, suggesting the franc was overvalued by roughly 378% on a Big Mac basis. In practice, such extremes reflect differences in labor costs, real estate, and local market conditions rather than pure currency misalignment.

Central Bank Intervention

Central banks hold foreign exchange reserves—primarily U.S. dollars—and deploy them to influence their currency's value. Total global reserves stood at approximately $12.4 trillion in 2023.

• Buying domestic currency: Sells foreign reserves to prop up a weakening currency (Japan spent $42 billion defending the yen in 2022)
• Selling domestic currency: Buys foreign currency to prevent appreciation that harms exports (Switzerland, China)
• Verbal intervention: Central bank officials signal intentions, causing traders to adjust positions preemptively
• Capital controls: Restrict money flowing in or out to reduce speculative pressure

Intervention works best when it aligns with fundamentals. Japan's 2022 yen interventions slowed depreciation temporarily but couldn't reverse it while U.S. interest rates continued rising above Japanese rates. Markets are bigger than any central bank's reserves.

The Dollar's Reserve Currency Status

The U.S. dollar accounts for approximately 59% of global foreign exchange reserves, down from 72% in 2000 but still dominant. About 88% of all foreign exchange transactions involve the dollar on one side. Oil, most commodities, and a majority of international trade contracts are denominated in dollars.

This "exorbitant privilege"—a term coined by French finance minister Valéry Giscard d'Estaing in the 1960s—allows the U.S. to borrow cheaply because foreign governments and institutions have structural demand for dollar-denominated assets. It also means Federal Reserve policy decisions ripple through every economy on Earth. When the Fed raises interest rates, emerging market currencies weaken as capital flows toward higher-yielding dollar assets—a pattern called the "dollar wrecking ball."

Can Exchange Rates Be Predicted?

Short answer: not reliably. Academic research since Meese and Rogoff's seminal 1983 paper has consistently found that economic models fail to outperform a simple random walk in forecasting exchange rates over horizons shorter than one to two years. Professional currency forecasters—employed by the world's largest banks—have track records that are, on aggregate, no better than chance.

Over longer horizons, fundamentals reassert themselves. Currencies of countries with persistently high inflation tend to depreciate. Countries with current account surpluses tend to see appreciation. But the path between today's rate and the eventual equilibrium is noisy, unpredictable, and littered with the wreckage of confident predictions. That's why $7.5 trillion changes hands every day—disagreement about the future is the fuel that powers the market.

Disclaimer: This article is for informational purposes only and does not constitute financial advice. Currency markets carry significant risk. Consult a qualified professional before making investment decisions.