Remember the two essential characteristics of pure public goods:
1. non-excludability meaning that no one (not even "non-payers" or what's referred to as "free-riders") can be excluded from consuming the good or service
2. Non-depletability meaning that an additional consumer won't diminish the amount left over for someone else
To be considered a pure public good, both characteristics must hold!
To see the difference between "public" and "private" goods, first consider a private good such as the purchase of a movie ticket. Since non-payers will not be allowed in the theater, non-payers (i.e., free-riders) are excluded from consuming the good; therefore, the non-excludability characteristic does not hold.
Also with private goods, such as a new automobile or a stereo, when someone makes a purchase, there is one less car or stereo left over to sell to someone else; therefore, the non-depletablity characteristic does not hold.
Can you think of a good or service for which only one of the two above characteristics holds? Name any examples that you can think of.
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Now consider public tv and radio, both good examples of public goods. Can anyone be excluded from watching public tv or listening to public radio? Does the non-excludability characteristic hold?
If one more person turns on their radio or tv, is there less product available for others? Does the non-depletability characteristic hold?
Can you name some other examples of public goods? There are several.
