Production possibility curves
Production possibility curves: build the core model, apply it to evidence and qualify conclusions where outcomes depend on context.
9708 section 1.5; AS Level. Checked against Cambridge's 2026–2028 Version 2 (latest version published December 2025) and 2029 Version 1 (published September 2026). Cambridge states that neither version has significant changes affecting teaching. Always follow the syllabus for the candidate's examination year.
Before you begin
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does a point beyond a current PPC indicate?
What you will learn
- Interpret feasible and unattainable output combinations
- Explain constant and increasing opportunity cost
- Analyse PPC shifts and points inside the curve
Core model and terms
A PPC shows maximum combinations of two outputs possible with current resources and technology. A point on the curve is productively efficient in the model; a point inside may show unused resources or inefficiency; a point outside is currently unattainable.
Apply and evaluate
A movement along the curve reallocates resources and has an opportunity cost. A straight frontier can represent constant opportunity cost; a bowed frontier can represent increasing cost as increasingly unsuitable resources move between outputs. More or better resources or technology can shift the frontier.
Pause and explain
Which statement best applies production possibility curves?
Worked example
A country moves on its PPC from 40 to 50 units of food while machinery falls from 80 to 70. Interpret the trade-off.
Show the worked solution
- Food rises by 10
- Machinery falls by 10
- In this interval the opportunity cost is 10 machinery units
Answer Food rises by 10 → Machinery falls by 10 → In this interval the opportunity cost is 10 machinery units
Try a topic test
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A country moves on its PPC from 40 to 50 units of food while machinery falls from 80 to 70. Interpret the trade-off.
Give me a hint
Identify the relevant idea in production possibility curves, then trace the economic chain.
Compare my reasoning
- Food rises by 10
- Machinery falls by 10
- In this interval the opportunity cost is 10 machinery units
Food rises by 10 Machinery falls by 10 In this interval the opportunity cost is 10 machinery units
Look for these in your work
- Food rises by 10
- Machinery falls by 10
- In this interval the opportunity cost is 10 machinery units
A point lies inside a country’s PPC. State what it may show and one limit of that inference.
Give me a hint
Distinguish a model interpretation from a proven cause.
Compare my reasoning
- The combination is feasible
- Resources may be underused
- The curve alone does not identify why
The combination is feasible Resources may be underused The curve alone does not identify why
Look for these in your work
- The combination is feasible
- Resources may be underused
- The curve alone does not identify why
A new technology improves both industries. Explain the likely PPC change.
Give me a hint
Consider maximum feasible output rather than current production.
Compare my reasoning
- Productive capacity rises
- More combinations become feasible
- The frontier shifts outward
Productive capacity rises More combinations become feasible The frontier shifts outward
Look for these in your work
- Productive capacity rises
- More combinations become feasible
- The frontier shifts outward
A country moves along a bowed PPC toward renewable energy. Explain why the next units may have a higher opportunity cost.
Give me a hint
Consider increasingly specialised resources.
Compare my reasoning
- Initially suitable resources move first
- Further units require less suitable inputs
- More of the other output may be forgone
Initially suitable resources move first Further units require less suitable inputs More of the other output may be forgone
Look for these in your work
- Initially suitable resources move first
- Further units require less suitable inputs
- More of the other output may be forgone
Common mistakes
- Calling a point inside the PPC impossible or confusing a movement with a shift.
What can you explain now?
What does a point beyond a current PPC indicate?
Compare with the explanation
It is unattainable with current resources and technology
Points beyond the frontier require greater capacity; underuse is shown inside it.
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Make it stick
Before moving on, explain the central idea in production possibility curves and state one condition that could change its effect.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.