6.4 Exchange Rates


2026 Syllabus Objectives

By the end of this topic, you should be able to:

  1. Define what an exchange rate is
  2. Explain how a floating exchange rate is determined
  3. Distinguish between depreciation and appreciation of a floating exchange rate
  4. Explain the causes of changes in a floating exchange rate (demand and supply of the currency)
  5. Use AD/AS analysis to explain the impact of exchange rate changes on national income, real output, price level, and employment

1. What Is an Exchange Rate?

The exchange rate is the price of one country's currency expressed in terms of another country's currency. In other words, it tells you how much of one currency you need to buy a unit of another currency.

Example: If the exchange rate between Pakistan and the USA is 1 USD = 280 PKR, then one US dollar can buy 280 Pakistani rupees.

Think of it this way: just like a product has a price in a shop, a currency has a "price" too — and that price is the exchange rate.

The exchange rate represents the external value of a currency — how much it is worth compared to other currencies in the world.


2. How Is a Floating Exchange Rate Determined?

A floating exchange rate is one where the value of a currency is determined entirely by market forces — that is, by the demand for and supply of that currency in the foreign exchange market. The government does not interfere to set or fix the rate.

This works just like any other market. Think of the currency as a product:

  • If more people want to buy it (high demand), its price (exchange rate) goes up.
  • If more people want to sell it (high supply), its price goes down.

The Demand Curve for a Currency

The demand for a currency comes from foreigners who want to buy that country's goods, services, or assets. They need to exchange their own currency for the local currency.

The demand curve slopes downward — this means when the exchange rate is high (the currency is expensive), fewer foreigners want to buy it, so quantity demanded is lower.

The Supply Curve of a Currency

The supply of a currency comes from locals who want to buy foreign goods, invest abroad, or travel. To do this, they sell (supply) their own currency in exchange for foreign currency.

The supply curve slopes upward — when the exchange rate is high, locals find it cheap to buy foreign currency, so they supply more of their own currency.

Equilibrium Exchange Rate

Just like in any supply and demand diagram, the equilibrium exchange rate is found where the demand curve and the supply curve intersect. At this point, the quantity of currency demanded equals the quantity supplied.

📊 Diagram to Know: Draw a standard demand and supply graph. Label the vertical axis "Exchange Rate (ER)" and the horizontal axis "Quantity of Currency." The downward-sloping curve is Demand (D) and the upward-sloping curve is Supply (S). Where they cross is the equilibrium exchange rate.

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