AP Microeconomics / Imperfect Competition
Lesson
Monopoly output and price
One seller faces the market demand curve and restricts output to raise price.
Learning goals
- Find monopoly output and price from MR, MC, and demand.
- Explain why monopoly quantity is typically below the efficient quantity.
Explanation
A monopolist is the only seller of a good without close substitutes. To sell another unit, it usually must lower the price on units it was already selling, so marginal revenue sits below the demand curve. Output still satisfies MR = MC. Price is then read up to the demand curve, not off the MR curve.
That higher price and lower quantity create deadweight loss: some buyers value the good above MC but are not served. Barriers such as patents, control of a key input, or legal franchise help the position last. Barriers are a story about entry, not a moral score.
Key terms
- Market power. The ability to set a price above marginal cost without losing all customers.
- Price discrimination. Charging different prices to different buyers for the same product when costs do not justify the difference.
Common mistakes
- Setting price where MR = MC instead of reading price from demand.
- Assuming every monopolist earns a profit even when ATC is above demand.
Practice
Original Marlow Works items. Check the answer explanation after you try.
A binding price ceiling is set below equilibrium in the market for rental apartments. What is the most likely result?
Original Marlow Works item — not a College Board question.
Take your time—this is practice, not a test.
Answer explanation
Where does a single-price monopolist find the price it charges?
Answer. At the demand curve above the MR = MC quantity.
MR = MC picks quantity. Buyers’ willingness to pay at that quantity picks price.
Related resources
External links with reuse status. Marlow Works is independent and does not copy restricted exam or textbook material.
Official / link only
AP Microeconomics course page
Official six-unit framework for markets, costs, and market failure.
College Board · All rights reserved · accessed 2026-10-01
Open sourceCC BY — attribution required
Principles of Microeconomics: Scarcity and Social Provisioning
Open microeconomics background for scarcity, markets, and elasticity.
Open Textbook Library listing · CC BY · accessed 2026-10-01
Open source