The PPC and Economic Growth

Idea

Growth is shown on the PPC in two distinct ways. Actual growth is the expansion of an economy’s current output; potential growth is the expansion of its productive capacity — the maximum it could produce.

Mechanism

Actual growth — a movement from a point inside the PPC towards the curve. The economy puts previously idle or inefficiently used resources to work, so output of both goods rises with no change in capacity.
Potential growth — an outward shift of the whole PPC, driven by an increase in the quantity (more workers, more capital) or quality (better technology, more skilled labour) of resources. The frontier itself moves out, so combinations once unattainable become attainable.

An economy often needs both: potential growth raises the ceiling, and actual growth moves output up to it.

Diagram

Actual growth: the economy moves from an inefficient point A inside the PPC to point B on the curve, raising output of both goods as idle resources are brought into use.

Potential growth: an increase in the quantity or quality of resources shifts the PPC outward, from PPC to PPC¹, expanding productive capacity.

Considerations

The distinction maps directly onto macroeconomics: actual growth appears as a rise in real national income towards potential output on an AD–AS diagram, and potential growth as a rightward shift of long-run aggregate supply (Theme 3). A policy that builds capacity — investment, education, immigration — drives potential growth; one that raises demand for existing capacity drives actual growth.