A negative externality happens when the production or use of a product creates harmful effects for people who were not part of the original transaction. Because these people are not compensated for the harm, the total cost to society is higher than the cost paid by the producer.

This leads to over-production, as the market price does not reflect the true cost of things like pollution or health issues.

Examples:

• Production: Factory pollution, toxic waste, and mining damage.
• Consumption: Second-hand smoke, alcohol-related social costs, and noise pollution.

Key Economic Concepts:

• Private Marginal Cost (PMC): The cost paid directly by the producer.
• Social Marginal Cost (SMC): The total cost to society, including the harm done to others.
• When SMC is greater than PMC, the market produces too much, causing a deadweight loss to society.

Possible Government Solutions:

• Pigouvian Taxes: Putting a tax on harmful activities to align private costs with social costs.
• Regulations: Setting legal limits on pollution or banning harmful behaviors.
• Pollution Permits: Allowing companies to trade permits for limited emissions (Cap and Trade).
• Property Rights: Enabling people affected by negative impacts to claim damages.