How can a single curve show scarcity, choice, opportunity cost and growth all at once?
Use the production possibility curve to illustrate scarcity, choice, opportunity cost, efficiency and economic growth
A focused answer to the H2 Economics learning outcome on the production possibility curve. How the PPC shows scarcity, choice and opportunity cost, why it is usually concave, and how points on, inside and beyond it are interpreted.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
SEAB wants you to use the production possibility curve (PPC) to illustrate the core ideas of the subject: scarcity, choice, opportunity cost, productive efficiency and economic growth. The central insight is that one diagram captures the entire economic problem, so being fluent with it pays off across the whole course.
The answer
What the PPC shows
The production possibility curve shows the maximum combinations of two goods (or two categories of goods) that an economy can produce when all its resources are fully and efficiently employed, given current technology. Put consumer goods on one axis and capital goods on the other. The curve is the boundary of what is attainable.
Reading points on, inside and beyond the curve
Three regions carry distinct meanings:
- On the curve - the economy is using all its resources efficiently. Every such point is productively efficient: it is impossible to make more of one good without making less of the other.
- Inside the curve - resources are unemployed or used inefficiently, so the economy is producing less than it could. There is spare capacity.
- Beyond the curve - unattainable with current resources and technology. This region is exactly what scarcity means.
Opportunity cost along the curve
Moving from one point on the curve to another means producing more of one good and necessarily less of the other, because resources are fully employed. The amount of the second good given up is the opportunity cost of the extra units of the first.
Why the curve is concave
A PPC is usually drawn concave to the origin (bowed outward), reflecting the law of increasing opportunity cost. Factors of production are not equally suited to producing both goods. When an economy first switches resources toward one good, it moves the most suitable resources first; as it keeps expanding that good, it must use resources better suited to the other, so each extra unit costs more of the other good. A straight-line PPC would instead imply constant opportunity cost, meaning resources are perfectly substitutable between the two uses.
Shifts: growth and decline
An outward shift of the whole curve represents economic growth: combinations once unattainable become attainable. It is caused by an increase in the quantity or quality of resources, for example a larger labour force, investment in capital, or improved technology. An inward shift represents a fall in productive capacity, for example after a natural disaster or a fall in the labour force.
Examples in context
Example 1. Singapore choosing capital over consumption. Singapore's high savings and investment rates, channelled through compulsory saving and state investment, push the economy toward the capital-goods end of its PPC. The opportunity cost is lower present consumption, but the reward is a faster outward shift of the curve and stronger long-run growth.
Example 2. A pandemic shock. When a pandemic removes workers from the labour force through illness or restrictions, the economy moves inside its PPC as resources go idle, and in a severe case the curve can shift inward if capacity is permanently lost. Recovery is shown as a move back toward the curve as resources return to work.
Try this
Q1. What does a point inside the PPC represent? [2 marks]
- Cue. Unemployed or inefficiently used resources: the economy is producing less than its maximum, so it has spare capacity.
Q2. Explain why moving along a PPC involves an opportunity cost. [3 marks]
- Cue. Resources are fully employed on the curve, so producing more of one good requires transferring resources away from the other, and the output of the other good given up is the opportunity cost.
Q3. State two causes of an outward shift in the PPC. [2 marks]
- Cue. An increase in the quantity or quality of resources, for example a larger or better-educated labour force, more capital from investment, or improved technology.
Exam-style practice questions
Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Original10 marksUsing a production possibility curve, explain how the diagram illustrates scarcity, choice, opportunity cost and economic growth.Show worked answer →
A 10 mark question rewards a correctly described diagram and the explicit link from each feature to an economic concept.
- The diagram
- Draw a curve concave to the origin with consumer goods on one axis and capital goods on the other. The curve shows the maximum combinations of the two goods an economy can produce with its current resources and technology.
- Scarcity
- Points beyond the curve are unattainable with current resources, which is exactly what scarcity means.
- Choice
- Any point on the curve is a choice about how to allocate resources between the two goods.
- Opportunity cost
- Moving along the curve from one point to another means producing more of one good and less of the other; the quantity of the second good given up is the opportunity cost.
- Economic growth
- An outward shift of the whole curve, caused by more or better resources, shows economic growth: combinations once unattainable become attainable.
Markers reward correct axes and shape, points on, inside and beyond the curve correctly interpreted, and the outward shift labelled as growth.
Original8 marksExplain why a production possibility curve is normally drawn concave to the origin, and what a straight-line curve would imply.Show worked answer →
An 8 mark question rewards the law of increasing opportunity cost and a contrast with constant opportunity cost.
- Concave shape
- A concave curve reflects increasing opportunity cost. As an economy produces more of one good, it must transfer resources that are increasingly less suited to that good, so each extra unit costs more and more of the other good forgone.
- Why resources are not equally suited
- Factors of production are specialised. The first resources switched are the most suitable, but as production expands, less suitable resources must be used, raising the opportunity cost.
- Straight line
- A straight-line PPC would imply constant opportunity cost: resources are perfectly substitutable between the two goods, so each extra unit of one always costs the same amount of the other.
Markers reward the increasing-opportunity-cost reasoning, the link to factor specialisation, and the correct interpretation of a linear curve as constant opportunity cost.
Related dot points
- Explain scarcity as the fundamental economic problem, and show how it forces choice and gives every decision an opportunity cost
A focused answer to the H2 Economics learning outcome on scarcity, choice and opportunity cost. Why unlimited wants meet limited resources, why this forces choice, and how opportunity cost measures the true cost of any decision.
- Compare how market, planned and mixed economies allocate scarce resources and answer the what, how and for whom questions
A focused answer to the H2 Economics learning outcome on economic systems. How market, planned and mixed economies answer the what, how and for whom questions, and the strengths and weaknesses of each.
- Explain rational decision-making by economic agents using marginal analysis and the comparison of marginal benefit and marginal cost
A focused answer to the H2 Economics learning outcome on rational decision-making. How consumers, firms and governments weigh marginal benefit against marginal cost, and why decisions are made at the margin, not in totals.
- Distinguish actual from potential growth, explain the business cycle, and evaluate the benefits and costs of growth
A focused answer to the H2 Economics learning outcome on economic growth. The difference between actual and potential growth, the phases of the business cycle, the sources of each kind of growth, and the benefits and costs of growth.
- Distinguish positive from normative statements and explain the role of value judgements in economic analysis and policy
A focused answer to the H2 Economics learning outcome on positive and normative economics. How to tell a testable factual claim from a value judgement, and why the distinction shapes evaluation and policy debate.