Demand and Supply Theory and Equilibrium Exchange Rate

1. Foundations of the Demand and Supply Theory

Under the modern inconvertible paper currency system, the Demand and Supply Theory (also known as the Balance of Payments Theory of Exchange Rate) is the premier framework for understanding exchange rate movements in a market-determined floating regime.

Core Axiom:
The foreign exchange rate is the market price of one currency in terms of another, determined in a competitive foreign exchange market by the interaction of aggregate Demand for Foreign Exchange and aggregate Supply of Foreign Exchange.

Equilibrium Exchange Rate Condition:
Quantity Demanded for Forex (Qd) = Quantity Supplied of Forex (Qs)

2. Demand for Foreign Exchange

The Demand for Foreign Exchange represents the desire of domestic residents to purchase foreign currency (e.g., US Dollars) using domestic currency (Indian Rupees).

A. Economic Sources of Demand for Foreign Exchange:

1. Import of Physical Merchandise: Indian businesses importing crude oil, defense equipment, electronic components, industrial machinery, and gold must pay foreign suppliers in foreign currency (USD).
2. Import of Foreign Services: Paying foreign shipping companies for freight, foreign reinsurers, international streaming services, and foreign software licenses.
3. Outward Foreign Investments: Indian corporations acquiring overseas businesses (e.g., Tata purchasing Jaguar Land Rover in the UK) or domestic citizens investing in US stock markets via the Liberalised Remittance Scheme (LRS).
4. Overseas Travel, Education & Medical Care: Indian students paying tuition fees to American universities or Indian tourists spending abroad.
5. Debt Servicing & Interest Payments: Indian corporations and the government repaying principal and interest on External Commercial Borrowings (ECBs).
6. Speculative Demand: Currency traders buying foreign exchange in anticipation of future currency appreciation.

B. Why is the Demand Curve for Foreign Exchange Downward-Sloping?

The demand curve for foreign exchange (D) slopes downward from left to right, indicating an inverse relationship between the exchange rate and the quantity of foreign currency demanded:

• When the Exchange Rate (USD / INR) Falls (e.g., from 85 to 75 INR): Foreign currency becomes cheaper → Imported goods become cheaper in India → Indian consumers demand more imported goods → Quantity of US Dollars demanded increases.

• Conversely, when the Exchange Rate Rises (from 75 to 85 INR): Foreign currency becomes more expensive → Imports become costly in India → Quantity demanded contracts.

3. Supply of Foreign Exchange

The Supply of Foreign Exchange represents the inflow of foreign currency (US Dollars) entering the domestic economy, seeking conversion into domestic currency (Indian Rupees).

A. Economic Sources of Supply of Foreign Exchange:

1. Export of Physical Merchandise: Indian exporters selling refined petroleum, pharmaceutical formulations, textiles, and agricultural produce to foreign buyers.
2. Export of Invisible Services: Global revenues earned by Indian IT consulting companies (TCS, Infosys, Wipro) and business process outsourcing (BPO) centers.
3. Foreign Inward Remittances: Non-resident Indian (NRI) expatriates working in the Gulf, North America, and Europe remitting funds home to support families.
4. Foreign Capital Inflows: Foreign Direct Investment (FDI) in Indian manufacturing and services, plus Foreign Portfolio Investment (FPI) into the Bombay Stock Exchange (BSE) and National Stock Exchange (NSE).
5. Foreign Tourism & Inward Medical Travel: Foreign tourists and medical travelers visiting India, spending foreign exchange locally.
6. External Commercial Borrowings (ECBs): Indian companies raising foreign currency debt in international capital markets and converting proceeds into rupees.

B. Why is the Supply Curve for Foreign Exchange Upward-Sloping?

The supply curve of foreign exchange (S) slopes upward from left to right, reflecting a direct relationship between the exchange rate and the quantity of foreign currency supplied:

• When the Exchange Rate (USD / INR) Rises (e.g., from 75 to 85 INR): Foreign buyers obtain more rupees per dollar → Indian exports become cheaper abroad → Foreign demand for Indian exports expands → Inflow of US Dollars supplied to market increases.

• Conversely, when the Exchange Rate Falls (from 85 to 75 INR): Indian goods become relatively expensive abroad → Exports decline → Quantity of dollars supplied falls.

4. Determination of the Equilibrium Exchange Rate

In a free-market foreign exchange regime, the Equilibrium Exchange Rate is established at the intersection of the downward-sloping Demand curve and the upward-sloping Supply curve:

• If Exchange Rate Rises Above Equilibrium (e.g., 88.00 INR):
  At this higher price, Quantity Supplied of USD exceeds Quantity Demanded (Excess Supply of Forex). Unsold foreign currency forces dealers to lower the dollar price back down toward 84.00 INR.
• If Exchange Rate Falls Below Equilibrium (e.g., 80.00 INR):
  At this lower price, Quantity Demanded of USD exceeds Quantity Supplied (Excess Demand / Shortage of Forex). Intense competition among importers bids up the price of dollars back toward 84.00 INR.

5. Shifts in Equilibrium: Currency Appreciation vs. Depreciation

When economic fundamentals change, the entire Demand or Supply curve shifts, creating a new equilibrium exchange rate:

Comparative Matrix of Shifts: