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EC311 · Intermediate Microeconomics

EC311 / TOPIC 28

8.2 Price discrimination

How should a seller allocate output across customer groups when resale is blocked?

Allocate so each market’s MR equals common MC, then price from that market’s demand.

Follow the cause and effect

  1. Write separate demand and MR for each group.

  2. Set MR1=MR2=MC to find each Qi.

  3. Substitute Qi into demand and check that the less elastic group pays more.

The model you are using

KEY MODEL
P₁=100−Q₁
P₂=60−Q₂
MC=20
MR₁=MR₂=20

Conditions for this model

Two identifiable segments, no resale, constant MC and no extra segmentation fixed cost.

The exam trap

Different prices do not prove discrimination when service costs differ, and resale can undo price gaps.

Connect the reasoning to the graph

What changes

  • Two market panels have separate MR curves linked by one MC; total output is the sum of Qi.

What stays fixed

Two identifiable segments, no resale, constant MC and no extra segmentation fixed cost.

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

What to inspect

Substitute Qi into demand and check that the less elastic group pays more.

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 the more elastic group usually receives a lower price when MC is common.

Lesson references

  • Pindyck & Rubinfeld, Microeconomics, 9th Global ed., pp. 415, 418
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