In: Economics
A public good has two key characteristics: it is nonexcludable and nonrivalrous.
Nonexcludable means that preventing anyone from using a good is
expensive or impractical to one person.
Nonrivalous means that it doesn't prevent others from using it when
one person uses a good.
Examples of the public goods are a number of government
services. For example, providing fire and police service would not
be easy so some people in a neighborhood would be protected from
their property's burning and burglary while others would not be
protected at all. Protecting a few automatically requires still
protecting many.
Positive externalities and public benefits are terms which are
closely related. Public benefits have beneficial externalities,
such as support for policing or public health. Nevertheless not all
goods and services with favorable externalities are public goods.
Education investments ha ve significant positive spillovers but a
private corporation can have them.
Private companies can invest in new inventions like the Apple iPad, and make profits that may not capture all of the social benefits.