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Monopolistic Competition – Long-Run Equilibrium (Normal Profit)

HL Content
Microeconomics

A diagram illustrating a firm in monopolistic competition in long-run equilibrium, where it earns normal profit. The ATC curve is tangent to the demand curve (AR), meaning total revenue equals total cost.

Diagram
Monopolistic Competition – Long-Run Equilibrium (Normal Profit)
Curves and Elements

ar

AR = D: The average revenue or demand curve, downward sloping due to product differentiation.

mr

MR: Marginal Revenue, lies below AR because the firm must lower price to sell more.

mc

MC: Marginal Cost, intersects MR at the profit-maximizing output Qm.

atc

ATC: Average Total Cost, tangent to AR at Qm, indicating zero economic profit.

q

Qm: The output level where MR = MC.

p

Pm: The price corresponding to Qm on the AR curve.

Key Explanations
1

Firms in monopolistic competition face a downward-sloping demand curve (AR = D) due to product differentiation.

2

The profit-maximizing quantity is found where marginal cost (MC) equals marginal revenue (MR).

3

The corresponding price (Pm) is determined by extending a line from Qm up to the AR curve.

4

In the long run, the ATC curve is tangent to the AR curve at Qm, indicating that the firm earns normal profit (no economic profit).

5

This outcome results from the entry of new firms eroding any abnormal profits that existed in the short run.

Example Exam Question

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