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EC311 · Intermediate Microeconomics

EC311 / TOPIC 10

4.2 Giving and the price of a donation

How does donation matching change the price of helping recipients?

Matching makes one donor baht create more than one recipient baht, rotating the giving constraint.

Follow the cause and effect

  1. Define s as matching funds per donor baht.

  2. Write c+g/(1+s)=m to reveal the effective price of g.

  3. Solve choice and compare private outlay with recipient receipts.

The model you are using

KEY MODEL
c + g/(1+s) = m
U = √(cg)

Conditions for this model

Original model: donor values total receipts, with no matching cap or crowding out of other donors; no claim about current tax rules.

The exam trap

Do not confuse recipient receipts g with the donor outlay g/(1+s).

Connect the reasoning to the graph

What changes

  • More matching expands the g-intercept while leaving the c-intercept fixed.

What stays fixed

Original model: donor values total receipts, with no matching cap or crowding out of other donors; no claim about current tax rules.

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

What to inspect

Solve choice and compare private outlay with recipient receipts.

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

5 MINUTES · TRANSFER THE IDEA

Can you explain it without the lesson?

If matching falls from one-for-one to half-for-one, explain the budget rotation.

Lesson references

  • Original application of VA consumer budget/choice framework
  • Perloff, Microeconomics, 7th ed., p. 103 (altruism topic; no exercise text reproduced)
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