Why Forex Is the Pricing Language of Global Capital Flows
Forex is not merely the exchange of one form of cash for another. It is the currency pricing system jointly used in global trade, cross-border investment, bond issuance, corporate mergers and acquisitions, central bank reserves and international payments. Foreign exchange trading (FX) determines the relative prices between different currencies, as well as the exchange rate costs that capital must bear when moving between countries.
From an international finance perspective, the exchange rate is a bridge connecting domestic prices and international prices. Importers need to use their domestic currency to buy foreign currency for payments, exporters need to convert foreign currency revenue back into domestic currency, and investors must also complete currency conversion before buying overseas stocks or bonds. Therefore, exchange rate movements affect commodity prices, corporate profits, asset valuations and portfolio performance.
The global forex market is primarily an over-the-counter (OTC) market, where counterparties usually execute transactions through quotes from banks, brokers, electronic trading platforms and financial institutions. Unlike centralized exchanges, the forex market has no single central price. Quotes from different banks and platforms may vary slightly due to liquidity, client type, trade size and risk control rules.
Main Participants in the Forex Market
Commercial banks: Provide quotes, settlement, market making and client currency exchange services.
Central banks: Influence the exchange rate environment through reserve management, intervention operations and monetary policy.
Corporations: Generate real foreign exchange demand through imports and exports, overseas revenue and cross-border payments.
Asset managers: Generate currency exposure through global allocations to equities, bonds and commodities.
Individual clients: Generate forex demand through travel, overseas study, remittances, deposits and investment.
Understanding Exchange Rate Changes Through Quotation Methods
Direct Quotation and Indirect Quotation
Direct quotation expresses the price of 1 unit of foreign currency in terms of the domestic currency. For example, USD/TWD at 32.50 means that 1 U.S. dollar requires 32.50 New Taiwan dollars. Most Asian markets are more accustomed to using direct quotation in everyday explanations.
Indirect quotation expresses the price of 1 unit of domestic currency in terms of foreign currency. For example, if the British pound is used as the base, the quote may indicate how many U.S. dollars 1 pound can be exchanged for. In international markets, the euro, British pound, Australian dollar and New Zealand dollar are commonly quoted with themselves as the base currency.
Understanding the quotation direction is important. Under direct quotation, a rise in the numerical value usually indicates depreciation of the domestic currency, because more domestic currency is needed to buy 1 unit of foreign currency. Under indirect quotation, a rise in the numerical value usually indicates appreciation of the domestic currency, because 1 unit of domestic currency can be exchanged for more foreign currency.
| Quotation Method | Key Parameters | Applicable Scenarios | Main Risks |
|---|---|---|---|
| Direct Quotation | Domestic currency amount ÷ 1 unit of foreign currency | Market explanations for the New Taiwan dollar, Japanese yen, renminbi and similar currencies | A rising value is often misread as domestic currency strength |
| Indirect Quotation | Foreign currency amount ÷ 1 unit of domestic currency | Quotation conventions for the euro, British pound, Australian dollar and similar currencies | The base currency must be confirmed first |
| Bid-Ask Quote | Bid price, ask price, spread | Bank currency exchange and trading platform quotes | Excessively wide spreads increase trading costs |
| Cross Rate | Conversion through a third currency | Exchange between non-USD currencies | Multiple conversions may increase errors and costs |
Exchange Rate Differences, Interest Rate Differentials and Theoretical Foundations
Exchange Rate Difference: The Result of Price Fluctuations
Exchange rate differences arise from different exchange rates at the time of purchase and sale. The calculation can be expressed as: domestic currency result = foreign currency amount × exchange rate at sale - domestic currency cost at purchase - related fees. If the result is positive, it indicates a positive difference caused by exchange rate movements; if the result is negative, it indicates a foreign exchange loss.
Exchange rate differences are affected by multiple factors, including central bank interest rates, inflation differentials, economic growth, current accounts, fiscal conditions, political risk and risk appetite. In the short term, market sentiment and capital flows may dominate exchange rates; over the long term, inflation and changes in purchasing power also affect currency value.
Interest Rate Differentials and Interest Rate Parity
An interest rate differential is the difference between the interest rates of two currencies. Carry trades usually involve borrowing a low-interest-rate currency and holding a high-interest-rate currency, or holding higher-yielding currency assets in an account. However, the interest rate differential does not equal the final return, because exchange rate fluctuations may exceed the interest difference.
John Maynard Keynes discussed the relationship between interest rates, forward exchange rates and currency expectations inA Tract on Monetary Reformin 1923. The later interest rate parity framework holds that the difference between the forward exchange rate and the spot exchange rate is influenced by the interest rate differential between two currencies. A simplified expression is: forward exchange rate ≈ spot exchange rate × pricing currency interest rate factor ÷ base currency interest rate factor.
Gustav Cassel’sPurchasing Power Parity Theory, proposed in 1918, emphasizes that long-term exchange rates are related to price levels and inflation differentials across economies. This theory is suitable for explaining long-term changes in currency purchasing power, but in short-term trading it is often disrupted by capital flows, interest rate expectations and risk sentiment.
| Comparison Dimension | Key Parameters | Applicable Scenarios | Main Risks |
|---|---|---|---|
| Exchange Rate Difference | Purchase exchange rate, sale exchange rate, fees | Exchange rate fluctuation analysis | Incorrect directional judgment may lead to losses |
| Interest Rate Differential | Interest rates of two countries, holding period, financing costs | Deposits, bonds and carry trades | High-interest-rate currencies may depreciate |
| Interest Rate Parity | Spot exchange rate, forward exchange rate, interest rate differential | Forward pricing and hedging analysis | Deviations may occur under market stress |
| Purchasing Power Parity | Price levels, inflation differentials, long-term equilibrium | Long-term exchange rate valuation | Limited explanatory power in the short term |
The U.S. Dollar System and the U.S. Dollar Index
Why the U.S. Dollar Has Global Influence
The global status of the U.S. dollar comes from multiple factors. After World War II, the Bretton Woods system established an international monetary arrangement centered on the U.S. dollar. The dollar was once linked to gold, while other major currencies maintained fixed exchange rates against the dollar. After the United States stopped converting dollars into gold in 1971, major economies gradually entered the era of floating exchange rates. However, the dollar has maintained significant influence due to the scale of U.S. financial markets, the liquidity of U.S. Treasury securities, payment and clearing networks and commodity pricing conventions.
The petrodollar system is often used to explain the relationship between the U.S. dollar and energy trade. More precisely, global crude oil and most commodities have long been commonly quoted and settled in U.S. dollars, reinforcing the demand for dollar liquidity among companies and central banks worldwide. However, this does not mean that all energy transactions are legally required to use the U.S. dollar. Rather, it is the result of market conventions, financial infrastructure and liquidity working together.
How DXY Measures U.S. Dollar Strength
The U.S. Dollar Index (DXY) measures changes in the U.S. dollar relative to a basket of six major currencies. DXY is heavily weighted toward the euro, so it is more suitable for observing the strength of the U.S. dollar relative to major developed-market currencies. It should not be directly equated with the dollar’s overall performance against all currencies.
| Currency Component | Key Parameters | Applicable Scenarios | Main Risks |
|---|---|---|---|
| Euro | Weight: 57.6% | Assessing differences between the U.S. dollar and the European economic cycle | The euro’s high weighting may dominate the index direction |
| Japanese Yen | Weight: 13.6% | Observing interest rate differentials and safe-haven conditions | Changes in Japanese policy may quickly affect the index |
| British Pound and Canadian Dollar | Weights: 11.9% and 9.1% | Supplementary observation of financial and commodity currencies | Events in the UK and energy markets may cause disruptions |
| Swedish Krona and Swiss Franc | Weights: 4.2% and 3.6% | Observing changes in supplementary European currencies | Lower weighting limits the explanatory scope |
How the U.S. Rate-Hike Cycle Affects the Forex Market
The Federal Reserve’s rapid rate hikes in 2022 are a typical case for observing the relationship between interest rates and exchange rates. As U.S. interest rates rose, the nominal yield on dollar assets increased, and some global capital flowed back into dollar assets. DXY reached elevated levels during that year. The euro, Japanese yen and some emerging market currencies came under pressure due to widening interest rate differentials, energy shocks or capital outflow pressure.
This case shows that exchange rate movements are not determined by a single data point. Interest rates are an important variable, but inflation expectations, fiscal conditions, balance of payments, risk appetite and geopolitical events also jointly affect capital flows. A professional understanding of the forex market should move from judging isolated rises and falls to a multi-factor framework.
Four Levels of Forex Analysis
First, confirm the quotation method to avoid misunderstanding the direction of currency appreciation or depreciation.
Next, analyze interest rates, inflation and central bank policy to assess changes in funding costs.
Continue by observing the current account, capital account and foreign exchange reserves to understand long-term supply and demand.
Finally, combine market risk sentiment and liquidity conditions to assess short-term volatility risk.
Questions Related to Forex and Capital Flows
Why does the forex market affect global asset prices?
Because cross-border capital usually needs to complete currency conversion before entering stock, bond, commodity or real estate markets. Exchange rate movements affect funding costs, translated asset returns and the risk appetite of international investors.
Can the U.S. Dollar Index represent the performance of all currencies against the dollar?
No. DXY only covers six major currencies and has a high euro weighting. Movements in emerging market currencies, the renminbi and commodity currencies need to be observed through other indices or specific currency pairs.
Is a currency with a higher interest rate necessarily stronger?
Not necessarily. Higher interest rates may attract capital inflows, but if the market is concerned about inflation, debt, political risk or recession, a high-interest-rate currency may still depreciate.
Is purchasing power parity suitable for short-term trading?
Purchasing power parity is more suitable for long-term valuation analysis. Short-term exchange rates are often affected by interest rate expectations, capital flows and risk sentiment, so short-term direction cannot be judged solely by price level differences.
