ECShiftGraph.Shock · Shift(s) · Result
← Course home

EC311 · Intermediate Microeconomics

EC311 / TOPIC 32

8.6 Bertrand, price leadership and cartels

How do price competition, leadership, and cartels differ in strategic variables?

Bertrand tests undercutting, a leader faces residual demand, and a cartel allocates joint output like multiple plants.

Follow the cause and effect

  1. Identify product differentiation and whether firms choose P or Q.

  2. For price leadership, build residual demand=market demand−fringe supply.

  3. For a cartel, set joint MR=MCi and inspect each firm’s deviation.

The model you are using

KEY MODEL
Qd=100−P
Sf=P−20
Qleader=120−2P
MRleader=60−Qleader

Conditions for this model

The leader example has P≥20 and MCleader=20. Bertrand uses its own separately stated assumptions.

The exam trap

The Bertrand P=MC result needs homogeneous goods, similar costs, and no binding capacity constraints.

Connect the reasoning to the graph

What changes

  • A price leader graph uses residual demand after fringe supply; a cartel uses market demand and total output.

What stays fixed

The leader example has P≥20 and MCleader=20. Bertrand uses its own separately stated assumptions.

Keep these conditions throughout the comparison; change only what the case above specifies.

What to inspect

For a cartel, set joint MR=MCi and inspect each firm’s deviation.

Compare before and after, and locate the conclusion on the graph.

5 MINUTES · TRANSFER THE IDEA

Can you explain it without the lesson?

Explain why a cartel can maximize joint profit yet remain unstable when members can expand output.

Lesson references

  • Pindyck & Rubinfeld, Microeconomics, 9th Global ed., pp. 478, 490
32/43