Price Ceiling
What is Price Ceiling?
A price ceiling is a government-imposed maximum price that can be charged for a good or service.
Price ceilings are typically set below the equilibrium price to make essential goods more affordable. However, they can lead to shortages, as quantity demanded exceeds quantity supplied at the ceiling price.
Price Ceiling: a worked example
A city council caps the price of gasoline. Market demand is Qd = 90 - 10P and supply is Qs = 20P - 30, with P in dollars per gallon and Q in thousands of gallons. Setting them equal, 90 - 10P = 20P - 30, so 120 = 30P and the equilibrium price is $4 with 50 thousand gallons traded. The council imposes a ceiling of $3. At that price, Qd = 90 - 30 = 60 and Qs = 60 - 30 = 30, so the shortage is 60 - 30 = 30 thousand gallons. Only 30 thousand gallons actually change hands, because the short side of the market determines the quantity transacted. Had the council chosen $5 instead, the ceiling would sit above equilibrium and nothing would change, since $4 is already a legal price.
The mistake students make with price ceiling
The most costly error is drawing the ceiling above the equilibrium price and then describing a shortage. A ceiling above equilibrium is non-binding, the market clears on its own, and quantity and price stay put. The second error is reporting the amount exchanged as the quantity demanded at the ceiling. Producers cannot be compelled to make more, so the amount traded is the smaller number, quantity supplied. On a graph question, place the ceiling line below equilibrium, mark quantity supplied on the left and quantity demanded on the right, and label the horizontal gap as the shortage.
Price Ceiling questions
Does a price ceiling always cause a shortage?
A price ceiling causes a shortage only when it binds, meaning it sits below the equilibrium price. At that legal maximum, quantity demanded exceeds quantity supplied and the horizontal gap between them is the shortage. A ceiling set above equilibrium is non-binding, because the market already clears at a price the law permits, so quantity, price, and total surplus are all unchanged.
What happens to consumer surplus under a price ceiling?
Consumer surplus can move in either direction. Buyers who still obtain the good pay less, which transfers surplus from producers to them. Fewer units trade, though, so buyers rationed out of the market lose their surplus entirely. Producer surplus always falls, and total surplus falls because of deadweight loss on the units no longer exchanged. Whether consumers gain overall depends on how sharply quantity contracts.
Why do price ceilings lead to queues and black markets?
Price normally rations a limited quantity toward the buyers who value it most. A ceiling forbids that, so something else takes over the rationing job: waiting in line, favoritism, lotteries, or side payments. Buyers still willing to pay far above the legal maximum then find sellers willing to break the rule, and an illegal secondary market forms at a price above the ceiling.
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Related terms
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