Externalities: When Is a Potato Chip Not Just a Potato Chip?

An “externality” occurs when a transaction between two people affects a third person without that person’s permission. Professor Michael Munger illustrates a simple externality problem with potato chips. If Art sells potato chips to Betty, Art and Betty are both better off. However, if Betty crunches her chips loudly enough that it annoys Carl, then Carl has to bear a cost (in the form of annoyance), despite not receiving any benefit from the potato chip exchange. In this example, the volume of Betty’s eating is an externality Carl has to endure.

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