16.4
A negative externality is a cost suffered by an unrelated third party due to an economic transaction.
The costs created by negative externalities are not reflected in the market price of a good.
Consider a coal-fired power plant. It sells electricity at a price that covers its private costs, such as fuel, labor, and capital. However, the production of electricity also releases pollutants. The health and environmental costs of pollution are not borne by the power plant or the electricity consumers but by society at large.
The graph's supply curve, which is also the private marginal cost, intersects with the demand curve, determining the market quantity and price.
However, the social marginal cost, which includes the external marginal cost of pollution, is higher than the plant's private marginal cost.
At the socially optimal price, electricity would be more expensive. As a result, the socially optimal quantity will be less than the market quantity.
The deadweight loss triangle shows the loss of social welfare, when negative externality costs are not reflected in the market transaction, and too many units of electricity are produced.
A negative externality occurs when an economic transaction imposes unintended costs on third parties who are not directly involved in the market trans…
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