How Foreign Exchange Rates Are Set — And Why They Move
Why did the US dollar strengthen 15% against the Pakistani rupee in 2023? Why does the Japanese yen weaken when the Fed raises interest rates? Currency markets move for surprisingly rational reasons — once you understand the underlying mechanics.
What Determines Exchange Rates
In the modern floating exchange rate system (used since 1971), currency values are determined primarily by supply and demand in global foreign exchange (forex) markets. The forex market trades over $6.6 trillion DAILY — the largest financial market in the world. But what drives that supply and demand?
Interest Rate Differentials
The single most powerful driver of currency values is interest rate differentials between countries. When a country's central bank raises interest rates, its currency typically strengthens because: global investors move money to that currency to earn higher returns, creating demand that pushes the exchange rate up.
This is why when the US Federal Reserve raises rates, the dollar strengthens against virtually all currencies simultaneously — including the euro, pound, and rupee.
Inflation Rates
Countries with higher inflation experience currency depreciation over time. This is described by Purchasing Power Parity (PPP) theory: a currency's exchange rate adjusts so that a basket of goods costs the same in different countries. If Pakistan has 20% inflation while the US has 4%, the rupee should weaken by approximately 16% annually to maintain PPP.
Economic Performance and Growth
Strong economic growth attracts foreign investment — both direct investment (building factories) and portfolio investment (buying stocks and bonds). Both require buying the local currency, which strengthens it. GDP growth surprises, employment data, and trade balance figures are all watched closely by forex traders.
Political Stability and Risk
Currencies of politically stable countries are considered "safe havens." During global crises, investors flee to the US dollar, Japanese yen, and Swiss franc — regardless of those countries' economic conditions. The dollar's role as the world's reserve currency gives it extraordinary strength during uncertainty.
Central Bank Interventions
Central banks can directly intervene in currency markets by buying or selling their own currency. Japan has intervened to weaken the yen when it became too strong for exporters. Some countries (China, Pakistan, Saudi Arabia) maintain semi-fixed or managed exchange rates, using foreign reserves to keep their currency within a target range.
Why This Matters for Ordinary People
Exchange rates affect everyone: the price of imported goods, the cost of international travel, the value of remittances sent home, and returns on international investments. Understanding the mechanics helps you make better decisions about when to exchange currency, how to price international transactions, and how to think about global investments.