3.8

Long-Run Equilibrium and Efficiency in Perfect Competition

AP Microeconomics

The Long-Run Adjustment Process

Starting from Economic Profit

Starting from Economic Loss

12345678910111213141234567891011121314Market QuantityPriceInitial Eq.New Eq. (lower P)DS₁S₂ (after entry)

Entry shifts market supply right → price falls → profits eliminated

Long-Run Equilibrium Conditions

1234567891234567891011121314151617181920Quantity$/unitP = MC = min ATCMCATCP = MR = D = $7

Long-run equilibrium: P = MC = min ATC → allocative + productive efficiency + zero economic profit

Allocative Efficiency

Productive Efficiency

Why Zero Economic Profit?

Constant-Cost, Increasing-Cost, and Decreasing-Cost Industries

Efficiency Summary

AP Exam Tips

Common Mistakes