The Production Possibilities Frontier

A production possibilities frontier (PPF) turns scarcity into a diagram. It shows the maximum combinations of two outputs an economy can produce when its resources, technology, and institutions are fixed and productive capacity is used efficiently.

Build a frontier from a production schedule

Suppose a community kitchen can make bread and soup each day:

Plot bread horizontally and soup vertically, then connect the maximum-output combinations. Points on the frontier are feasible and productively efficient. Points inside are feasible but leave capacity unused. Points outside are unattainable under current conditions.

The slope measures opportunity cost

Moving along the frontier increases one output only by reducing the other. With bread on the horizontal axis and soup on the vertical axis, a segment's slope is:

The slope is normally negative. Its absolute value is the soup forgone per additional basket of bread. Moving from B to C adds 2 baskets and gives up 2 pots, so each additional basket costs 1 pot of soup.

Why a frontier is often bowed outward

A straight PPF represents constant opportunity cost. A bowed-out PPF represents increasing opportunity cost. Resources moved first are relatively well suited to bread; continued expansion eventually reallocates resources that are increasingly productive in soup.

A PPF is a snapshot of constraints. Moving along one frontier changes the output mix. A change in resources or technology shifts the whole frontier. These are different events.