Principles of Microeconomics / Unit 12 MIC 1109 short lesson, about 20 seconds
Public Goods: Nonexcludable and Non-Rival
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The idea
A public good has two properties. Nonexcludable: keeping a non-payer out is impossible or too costly. Non-rival: one person's use leaves as much for others, so the marginal cost of another user is zero.
In practice
Defense: nobody can be left out, and one more resident costs the army nothing.
Where people slip
Test both. A slice of pizza fails both; a crowded road fails one.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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