Question

Difficulty: HardForeign Exchange Market, Systems, and Exchange Rate Determination

In a foreign exchange market operating under a flexible exchange rate system, the quantity demanded of US Dollars (USD\text{USD}) in millions is given by Qd=12002EQ_d = 1200 - 2E, and the quantity supplied is given by Qs=400+3EQ_s = 400 + 3E, where EE is the exchange rate in Nigerian Naira per US Dollar (NGN/USD\text{NGN/USD}). If an increase in import demand shifts the dollar demand curve upward by 250250 million dollars at every exchange rate level, by how many Naira per Dollar will the equilibrium exchange rate increase?

Answer: 50 NGN/USD

Answer

The equilibrium exchange rate increases by 50 NGN/USD.
Under a floating exchange rate system, the equilibrium exchange rate is determined by the intersection of foreign currency supply and demand. Initially, setting 12002E=400+3E1200 - 2E = 400 + 3E yields E1=160 NGN/USDE_1 = 160\text{ NGN/USD}. When demand for foreign currency increases autonomously by 250250 million dollars, the demand curve shifts rightward to Qd=14502EQ_d' = 1450 - 2E. Equating this new demand with supply gives 14502E=400+3E    E2=210 NGN/USD1450 - 2E = 400 + 3E \implies E_2 = 210\text{ NGN/USD}. The net increase in the rate is 210160=50 NGN/USD210 - 160 = 50\text{ NGN/USD}.

Step-by-Step Solution

1
Find initial equilibrium exchange rate
E_1 = 160 NGN/USD
Equilibrium occurs where foreign exchange quantity demanded equals quantity supplied: 1200 - 2E = 400 + 3E.
2
Formulate new foreign exchange demand equation
Q_d' = 1450 - 2E
An autonomous increase in demand adds 250 million units to the existing demand function.
3
Find new equilibrium exchange rate
E_2 = 210 NGN/USD
Set the new demand equal to supply: 1450 - 2E = 400 + 3E.
4
Calculate the difference between the new and original exchange rates
210 - 160 = 50 NGN/USD
The question specifically asks for the increase in the equilibrium exchange rate.

Key Concept

Determination of Equilibrium Exchange Rates and Demand Curve Shifts
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