External cost = negative externality: cost of an activity that falls on people other than those who pursue the activity.
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External benefit = positive externality: benefit of an activity received by people other than those who pursue the activity.
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Externality: external cost or benefit of an activity.
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Positional arms race: series of mutually offsetting investments in performance enhancement that is stimulated by a positional externality.
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Positional arms control agreement: agreement in which contestants attempt to limit mutually offsetting investments in performance enhancement.
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