1.6

Market Equilibrium, Disequilibrium, and Changes in Equilibrium

AP Microeconomics

Market equilibrium

123456789101112123456789101112QuantityPrice ($)Equilibrium (Pe, Qe)DemandSupply

Equilibrium: where supply meets demand at P = $5, Q = 5

Solving for equilibrium algebraically

Disequilibrium

Surplus (excess supply)

123456789101112123456789101112QuantityPrice ($)Qd = 3Qs = 7DemandSupplyPrice = $7

At P = $7: Qs (7) > Qd (3) → Surplus of 4 units

Shortage (excess demand)

123456789101112123456789101112QuantityPrice ($)Qd = 7Qs = 3DemandSupplyPrice = $3

At P = $3: Qd (7) > Qs (3) → Shortage of 4 units

Self-correcting mechanism

Changes in equilibrium

Demand shifts (supply constant)

123456789101112123456789101112QuantityPrice ($)Old EqNew EqSupplyD₁D₂ (increase)

Demand increase → higher price and higher quantity

Supply shifts (demand constant)

123456789101112123456789101112QuantityPrice ($)Old EqNew EqDemandS₁S₂ (increase)

Supply increase → lower price and higher quantity

Double shifts (both curves shift)

Summary table of all single shifts

AP exam tips for 1.6

Common mistakes

Key equations

Vocabulary