Who pays for a warning everyone hears?
Can a project be worth doing even when no one wants to pay for it alone?
Ask two questions: does one person’s use leave less for someone else, and can nonpayers feasibly be excluded? A public good combines nonrival use with nonexcludability. The label does not simply mean government funded.
Try the fictional case
Three fictional households are considering one neighborhood warning siren. Once installed, all three hear it; one household hearing it does not reduce another’s access. It costs $45 for the period. The table gives assumed dollar benefits for that same period, not surveyed real values.
| Household | Assumed benefit | Equal cost share |
|---|---|---|
| A | $30 | $15 |
| B | $20 | $15 |
| C | $10 | $15 |
- Calculate total assumed benefit and total benefit minus the $45 cost.
- Would every household gain under an equal $15 contribution? Show each household’s benefit minus its contribution.
A simple 20 minute plan
Spend 4 minutes on the opening question, 8 on the table and calculations, 5 comparing explanations, and 3 on an exit ticket: “My conclusion is ____. One assumption that matters is ____.”
Open teacher answers
- Total benefit is $60. Net benefit is $60 minus $45 = $15 for the group under the stated assumptions.
- A gains $15, B gains $5, and C loses $5. A positive group total does not mean that every payment rule makes everyone better off.
A public good is not the same as any public service. A public school seat can be congested, and a public agency can sell a rival good. Classify the good’s properties, not its owner.
Teacher answer guide
- Total benefit is $60. Net benefit is $60 minus $45 = $15 for the group under the stated assumptions.
- A gains $15, B gains $5, and C loses $5. A positive group total does not mean that every payment rule makes everyone better off.
A public good is not the same as any public service. A public school seat can be congested, and a public agency can sell a rival good. Classify the good’s properties, not its owner.
State the limit
Benefits are assumed to be measurable and additive in dollars. The exercise does not measure safety, rights, fairness, or willingness to pay in a real neighborhood. No actual money should be collected from learners.
Further reading: OpenStax: public goods. Activities and examples are original to World Economy. A reference does not imply endorsement.
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