Question

Difficulty: HardPrice Controls: Ceilings and Floors

The market demand and supply equations for fertilizer in an agricultural district are given by Qd=1,80040PQ_d = 1,800 - 40P and Qs=200+40PQ_s = 200 + 40P, where PP is the price per bag in Naira (N\text{N}) and QQ is the quantity in bags. The government introduces a price ceiling of N12\text{N} 12 per bag to lower farming input costs. By how many bags does the quantity of fertilizer actually traded in the market decrease as a result of this price control policy?

Answer: 320 bags

Answer

The quantity of fertilizer actually traded in the market decreases by 320 bags.
Prior to government regulation, free market equilibrium is established where quantity demanded equals quantity supplied (1,80040P=200+40P1,800 - 40P = 200 + 40P), yielding an equilibrium price of 2020 Naira and an equilibrium volume of 1,0001,000 bags. When a maximum price ceiling of 1212 Naira is imposed, quantity demanded expands to 1,3201,320 bags while quantity supplied shrinks to 680680 bags. Because trade is voluntary, the quantity exchanged is constrained by the short side of the market (quantity supplied = 680680 bags). Comparing this volume to the initial equilibrium (1,0006801,000 - 680), the actual quantity of fertilizer traded decreases by 320320 bags.

Step-by-Step Solution

1
Determine the initial free-market equilibrium price and quantity
Pe=20P_e = 20 Naira and Qe=1,000Q_e = 1,000 bags
Equilibrium occurs where quantity demanded equals quantity supplied (Qd=QsQ_d = Q_s).
2
Calculate quantity demanded and quantity supplied at the price ceiling of P=12P = 12
Qd=1,320Q_d = 1,320 bags and Qs=680Q_s = 680 bags
Lowering the price below equilibrium increases buyer demand but disincentivizes supplier production.
3
Determine actual traded quantity using the short-side principle and calculate the volume change
Actual quantity traded =680= 680 bags; Reduction =1,000680=320= 1,000 - 680 = 320 bags
In a market economy, trade requires voluntary exchange; buyers cannot purchase more than suppliers offer at the regulated price ceiling.

Key Concept

Short-Side Rule and Contraction of Market Traded Volume under Price Ceilings
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