Chapter 17: Externalities – Microeconomics Study Notes

Externalities

Introduction to Externalities

Externalities are a central concept in microeconomics, describing situations where the actions of individuals or firms have effects on third parties that are not reflected in market prices. These effects can be either positive or negative, leading to market failures if left unaddressed.

• Externality: A cost or benefit arising from production or consumption that affects someone other than the decision-maker.

• Negative externality: Imposes a cost on others (e.g., pollution).

• Positive externality: Creates a benefit for others (e.g., vaccination).

Types of Externalities

• Negative production externalities: Harmful side effects from production (e.g., air pollution from factories).

• Positive production externalities: Beneficial side effects from production (e.g., bees pollinating nearby crops).

• Negative consumption externalities: Harmful side effects from consumption (e.g., secondhand smoke).

• Positive consumption externalities: Beneficial side effects from consumption (e.g., herd immunity from vaccines).

Negative Externalities: Pollution

Private, External, and Social Costs

• Private cost: Cost borne by the producer.

• Marginal private cost (MC): Cost of producing one more unit, paid by the producer.

• External cost: Cost imposed on others, not paid by the producer.

• Marginal external cost: Additional cost to others from one more unit produced.

• Marginal social cost (MSC): Total cost to society for one more unit produced.

Formula:

$MSC = MC + \text{Marginal external cost}$

Valuing External Costs

• External costs can be estimated by comparing market values (e.g., property values near clean vs. polluted rivers).

• Example: If homes by a clean river rent for $2,000/month and those by a polluted river for $1,500/month, the external cost of pollution is $500/month per home.

Market Equilibrium and Inefficiency

• In an unregulated market, firms ignore external costs, leading to overproduction and deadweight loss.

• Efficient outcome occurs where $MSC = MSB$ (marginal social benefit).

• Without intervention, $MC = MSB$ at a higher output, causing inefficiency.

Approaches to Correcting Negative Externalities

• Property rights: Assigning legal rights to resources can internalize externalities.

• Mandate clean technology: Regulations requiring pollution-reducing technologies.

• Tax or price pollution: Imposing taxes or creating markets for pollution permits.

Property Rights and Abatement

• Producers may adopt abatement technology or reduce output to minimize costs.

• Efficient market equilibrium is achieved when the supply curve reflects all social costs ($S = MC = MSC$).

Cap-and-Trade and Pigovian Taxes

• Pigovian tax: Tax equal to marginal external cost, aligning private and social costs.

• Cap-and-trade: Government sets a pollution cap and allows firms to trade permits, achieving efficiency.

Formula for Pigovian Tax:

$MC + \text{tax} = MSC$

Global Externalities

• Global problems (e.g., climate change) require international cooperation due to free-rider and carbon leakage issues.

The Coase Theorem

• If property rights are well-defined and transaction costs are low, private bargaining can resolve externalities efficiently, regardless of who holds the rights.

• High transaction costs or many parties make government intervention necessary.

The Tragedy of the Commons

Definition and Examples

The tragedy of the commons describes the overuse and depletion of common resources when users have no incentive to conserve. Examples include overfishing and overgrazing.

• Unsustainable use: Resource use exceeds renewal rate, depleting the stock.

• Inefficient use: Overuse leads to deadweight loss and reduced long-term benefits.

Solutions to the Tragedy of the Commons

• Property rights: Privatizing the resource aligns individual incentives with social efficiency.

• Production quotas: Limiting total use to sustainable levels.

• Individual transferable quotas (ITQs): Assigning and allowing trade of usage rights to achieve efficiency.

Positive Externalities: Education

Private and Social Benefits

• Private benefit: Benefit received by the consumer.

• Marginal private benefit (MB): Additional benefit from consuming one more unit.

• External benefit: Benefit received by others.

• Marginal external benefit: Additional benefit to others from one more unit consumed.

• Marginal social benefit (MSB): Total benefit to society from one more unit consumed.

Formula:

$MSB = MB + \text{Marginal external benefit}$

Market Failure and Government Intervention

• Markets underproduce goods with positive externalities, leading to deadweight loss.

• Government can intervene through:

  • Public provision: Government directly provides the good.

  • Private subsidies: Payments to private producers to encourage production.

  • Vouchers: Tokens given to consumers to purchase the good, increasing demand.

Efficiency and Challenges

• Efficient outcome occurs when the quantity produced equals the level where $MSC = MSB$.

• Public provision and subsidies can be inefficient due to bureaucratic inefficiency and lobbying.

• Vouchers can improve efficiency by promoting competition and consumer choice, but may be controversial.

Summary Table: Types of Externalities

Type	Production/Consumption	Example	Market Outcome
Negative	Production	Factory pollution	Overproduction
Positive	Production	Bees pollinating crops	Underproduction
Negative	Consumption	Secondhand smoke	Overconsumption
Positive	Consumption	Vaccination	Underconsumption