1.5 Production possibility curves
- Syllabus
- 9708–2026–2027
- Topic
- 1.5
- Level
- AS
Learning objectives
1.5.1Production possibility curve• Nature and meaning of a production possibility curve (PPC)1.5.2PPC shape and opportunity cost• Shape of the PPC: constant and increasing opportunity costs1.5.3PPC shifts• Causes and consequences of shifts in a PPC1.5.4Position within a PPC• Significance of a position within a PPC
What a production possibility curve shows
A production possibility curve (PPC) shows the maximum attainable combinations of two goods or services that an economy can produce when its available resources are fully and efficiently used.
For one PPC, the quantity and quality of resources, technology and relevant institutional conditions are held constant. Each axis measures the output of one good or category of goods.
Because resources are scarce, producing a different combination on the frontier requires reallocation. If an economy moves toward more machinery, labour and other resources must leave food production, so some food output is forgone.
The PPC shows productive possibilities, not which combination society ought to choose. It also does not show every detail of a real economy: it simplifies production to two outputs under stated constraints.
PPC shape and opportunity cost
Moving along a PPC shows the opportunity cost of gaining more output on one axis: the output on the other axis that must be forgone.
\text{Opportunity cost of extra }X=\frac{|\Delta Y|}{\Delta X}
If machinery output rises from 20 to 24 units while food falls from 90 to 82 units, the opportunity cost is ∣82−90∣/(24−20)=8/4=2 units of food per extra unit of machinery.
| PPC shape | Opportunity cost | Resource explanation |
|---|---|---|
| Straight line | Constant | Resources transfer between the two uses at a constant rate |
| Bowed outward from the origin | Increasing | Resources moved later are progressively less suited to the expanding use, so more of the other output is forgone |
The PPC normally slopes downward, so its numerical slope may be negative. Opportunity cost is reported as the positive amount forgone; a steeper segment therefore represents a larger opportunity cost of the horizontal-axis good.
A PPC shifts when resources, technology or institutions change
An outward PPC shift represents greater productive capacity; an inward shift represents reduced capacity. The cause may be a change in resources, labour skills, technology, infrastructure or institutional conditions.
A change affecting only one good can pivot or rotate the curve, while a broad improvement or shock can shift both intercepts. The curve does not move merely because the economy chooses a different point on it.
A new irrigation technology may increase the maximum food output and pivot the PPC outward toward food; a flood that destroys factories shifts machinery capacity inward.
Moving along a curve is reallocation; shifting the curve is a change in productive potential.
A point inside, on or outside a PPC has a different efficiency meaning
A point on a PPC represents productive efficiency: the available resources and technology are used to produce a maximum attainable combination. A point inside is attainable but inefficient; a point outside is currently unattainable.
The interpretation assumes the PPC’s resources, technology and institutional setting are fixed. An economy can move from inside towards the frontier by reducing unemployment or misallocation.
A country producing below its frontier may increase both food and machinery without a trade-off until it reaches the curve; moving along the curve then requires giving up one output.
A point outside is not “inefficient”—it cannot be produced with the current constraints.