Lesson plans · AP Macro Unit 1 · MACRO 1.1, MACRO 1.2, MACRO 1.3
Basic Macro Concepts: Scarcity, PPC, and Comparative Advantage
Essential question: If every economy faces scarcity, how do the PPC and comparative advantage let us measure the cost of a choice and the gains from trading it away?
2 × 50-minute periods · MACRO 1.1, MACRO 1.2, MACRO 1.3 · prints clean with Cmd/Ctrl+P
Objectives
- Students will be able to define scarcity and identify the four factors of production, distinguishing scarcity from a shortage.
- Students will be able to calculate opportunity cost from a production possibilities curve and from an output table.
- Students will be able to draw a bowed-out PPC and explain why its slope shows increasing opportunity cost.
- Students will be able to determine which producer holds the comparative advantage in each good and state a range of terms of trade that benefits both.
- Students will be able to classify an economy as market, command, or mixed by how it answers what, how, and for whom to produce.
Materials (all free, no student accounts needed)
Warm-up (8 min)
- Post on the board: 'You have $12 and one free hour after school. List everything you give up by spending both on a movie.' Give students 3 minutes to write silently.
- Cold-call four students for one sacrificed alternative each, then define the single next-best one they gave up as the opportunity cost. Everything they listed is scarcity; the one they would actually have chosen instead is the cost.
- State the day's line: every choice in this course has a cost, and the PPC is the tool that puts a number on it.
Direct instruction (22 min)
- Define scarcity as unlimited wants against limited resources, then name the four factors of production (land, labor, capital, entrepreneurship). Contrast scarcity (permanent, universal) with a shortage (temporary, price held below equilibrium) so students stop using them as synonyms.
- Read the 'Economic Systems' section of the lesson together and pull out the three questions every system answers: what, how, and for whom. Sort market, command, and mixed onto a spectrum, placing the US as mixed.
- Build a two-good PPC (pizzas vs robots) on the board. Mark a point on the curve (efficient), inside (unemployed resources), and outside (unattainable). Show that the slope between two points is opportunity cost.
- Explain why a bowed-out PPC means increasing opportunity cost: resources are not equally suited to both goods. Contrast with a straight-line PPC (constant cost).
- Introduce comparative advantage with a small output table. Convert to opportunity cost per one unit, and state the rule: lower opportunity cost wins, absolute advantage is irrelevant to who should specialize.
- Preview that circular flow and the business cycle (later in the lesson page) carry this vocabulary into Unit 2.
Guided practice (40 min)
- Project /sandbox/ppc on the board. With the class watching, drag a point from on the curve to inside it and cold-call: 'What does a point inside the frontier mean?' (idle or misused resources, a recession preview).
- Drag the point back onto the curve, then slide it down the frontier toward more of the x-axis good. Have students read off, in pairs, how many units of the y-axis good were sacrificed per unit gained. Call on two pairs for the opportunity-cost ratio.
- Grab the frontier itself and drag it outward. Ask the class to name three real causes of that shift (more resources, better technology, more capital) and label this as economic growth, not a movement along the curve.
- Split into whiteboard rounds: give each group an output table (Country A: 40 wheat or 20 cloth; Country B: 30 wheat or 30 cloth). Groups compute opportunity cost per unit, name each country's comparative advantage, and hold up boards on your count.
- Work the answer on the board: Country A gives up 0.5 cloth per wheat against Country B's 1 cloth, so A holds the comparative advantage in wheat; Country B gives up 1 wheat per cloth against A's 2 wheat, so B holds it in cloth. Have groups propose one terms-of-trade price for 1 wheat that leaves both better off, strictly between 0.5 and 1 cloth, for example 0.75 cloth. Point them to /calculate/comparative-advantage as the formula and method reference, not a live check.
Independent practice (25 min)
- Students complete a 10-question set on /practice/basic-macro-concepts filtered to scarcity, PPC, and comparative advantage, working alone.
- Each student sketches one bowed-out PPC by hand and writes one sentence explaining why its opportunity cost rises as you move down the curve.
Exit ticket
- A country can produce 100 phones or 50 laptops. State the opportunity cost of one laptop in phones.
- In one sentence, explain why a country can hold an absolute advantage in both goods but never a comparative advantage in both.
- Draw a PPC and mark a point that represents unemployed resources.
Homework
- Finish any remaining questions on /practice/basic-macro-concepts and read the Circular Flow section of the lesson to preview tomorrow.
- Write a half-page identifying whether your household allocates chores by market, command, or tradition, and defend the label.
Differentiation
- For students who finish early, hand them an input table (hours per unit) instead of an output table so they must flip the ratio to find comparative advantage.
- For strugglers, provide a pre-drawn PPC grid and have them only compute the slope between two labeled points before attempting a full sketch.
- Pair an English learner with a partner for the whiteboard rounds and accept the opportunity-cost ratio in numbers before requiring a full sentence.
Misconceptions to head off
- Belief: scarcity and shortage mean the same thing. Correction: scarcity is the permanent condition of limited resources; a shortage is a temporary market gap when price sits below equilibrium.
- Belief: the producer who makes more of a good should specialize in it. Correction: specialization follows comparative advantage (lower opportunity cost), not absolute advantage.
- Belief: a bowed-out PPC shows constant opportunity cost. Correction: concave-to-the-origin means opportunity cost increases; only a straight line is constant.
- Belief: moving to a point outside the current PPC is economic growth. Correction: growth is the whole curve shifting outward, not a jump to an unattainable point.
Teacher FAQ
- My students haven't taken micro. Is that a problem?
- No. This is the Unit 1 on-ramp and assumes nothing. If your class did take AP Micro, the PPC and comparative advantage are review, so compress direct instruction to 12 minutes and spend the extra time on the whiteboard trade rounds.
- The lesson page also covers circular flow and the business cycle. Should I teach those today?
- Not in this two-period plan. Those sections belong to Unit 2 (GDP and the business cycle). Assign them as preview reading for homework so the vocabulary is familiar when you start Unit 2.
- How should I grade the exit ticket?
- Two points for the correct opportunity-cost number with units (phones per laptop), one point for the absolute-vs-comparative sentence, one point for a PPC with a point drawn inside the curve. A student scoring 3 of 4 is ready to move on; 2 or fewer needs a reteach on opportunity-cost ratios.
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