Which describes a movement along the PPF?

• A. An outward shift of the frontier
• B. A change in productive capacity
• C. A change in the combination of goods produced using existing resources
• D. A shift of the entire frontier

Answer: (C)

Movement along the PPF happens when you change the mix of two goods produced while keeping resources and technology the same. You’re simply reallocating existing resources to produce more of one good and less of the other, so you stay on the same frontier curve. This trace along the curve reflects the opportunity cost of choosing more of one good over the other.

The other ideas describe shifts of the frontier itself: an outward shift means the economy can produce more in total due to more resources or better technology, which changes the frontier’s position. A change in productive capacity or a shift of the frontier also implies the overall potential output has changed, not just the mix along the existing curve.