AP Microeconomics / Basic Economic Concepts
Lesson
Comparative advantage and thinking at the margin
Specialize where your opportunity cost is lower, then decide one extra unit at a time.
Learning goals
- Identify comparative advantage from opportunity costs.
- Apply the rule that you expand an activity while marginal benefit exceeds marginal cost.
Explanation
Absolute advantage is about who can produce more. Comparative advantage is about who gives up less. Two people or countries can both gain from trade when they specialize in the good with the lower opportunity cost and then exchange.
Marginal analysis asks about the next unit, not the average of all units. Keep going while the extra benefit beats the extra cost. Stop when they meet. Sunk costs already spent should not steer the next yes-or-no.
Key terms
- Comparative advantage. The ability to produce a good at a lower opportunity cost than someone else.
- Marginal analysis. Comparing the extra benefit of one more unit with the extra cost of that unit.
Common mistakes
- Assigning specialization by who is faster, not by who gives up less.
- Letting a sunk cost decide whether to produce the next unit.
Practice
Original Marlow Works items. Check the answer explanation after you try.
Maya can spend Saturday tutoring for $80 or painting a mural that she values at $50 of enjoyment (and she cannot do both). What is her opportunity cost of tutoring, and why?
Original Marlow Works item — not a College Board question.
Take your time—this is practice, not a test.
Answer explanation
You already paid $12 for a ticket. A friend offers a free ride to a better show. What is the relevant cost of going to the original show?
Answer. The enjoyment you give up at the better show, not the $12 already spent.
The ticket price is sunk. The next choice is about alternatives still available.
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