A PPC is drawn for fixed resources and technology (Opportunity Cost Along the PPC). Over time those change, and so does the curve. The question to ask about any event: does it change what the economy can make, or only how much of it is being used?
Key idea
The PPC shifts outward (economic growth) when the economy gains resources, such as more workers, more capital or newly found natural resources, or better technology. It shifts inward when resources are lost, as in a disaster. Technology that helps only one good moves only that good's end of the curve. Putting idle resources back to work moves a point from inside the curve toward it; the curve itself stays put.
Why it works
The curve answers "what is the most we could make with everything we have and know?" More workers or machines, or a better way of making things, raise that maximum, so the curve moves out. Unemployed workers going back to work don't change the maximum; they were already counted as part of what the economy could use. So a recovery from a recession moves the economy's point, while growth moves the curve.
Worked example: Curve or point?
For a country making robots and wheat, what happens to its PPC or its position in each case? (a) A recession ends and laid-off factory workers are rehired. (b) Better education raises the skills of the whole workforce. (c) A new seed raises wheat output per acre, with no change in robot making.
- (a) The workers were already part of the economy's resources; they were idle. The point moves from inside toward the curve; the curve does not shift.
- (b) Workers can produce more of both goods: the whole curve shifts outward.
- (c) Only wheat production improves: the curve's wheat end moves out; the robot intercept stays.
Answer: (a) point moves toward the curve; (b) whole curve out; (c) wheat end out only.
Common mistake
Shifting the whole curve out when idle workers go back to work. That is a move from inside the curve toward it, not growth. Check: ask "does the economy now have more resources, or better technology, than before?" If it is only using more of what it already had, the curve doesn't move.
Choosing today matters for tomorrow. An economy that puts more of its resources into capital goods (machines, factories, training) instead of goods to consume now gives up some consumption today, but its PPC tends to shift out faster later.