Externalities & Public Goods

Externalities and Market Inefficiency

An externality arises when a market outcome affects parties other than the buyers and sellers in that market.

• Negative Externalities: Pollution
• Positive Externalities: Education

Whats the solution for Negative externalities?

• Direct Regulation: The government might mandate that all cars have catalytic converters or that a factory cannot dump more than a specific amount of chemicals into a river.
• Limitations: This is often inefficient because the government doesn’t know which firms can reduce pollution at a lower cost. It treats all firms the same, regardless of their technology.
• Corrective Taxes (Pigovian Taxes): A tax enacted to induce private decision-makers to take account of the social costs that arise from a negative externality.
  • An ideal corrective tax is equal to the External Cost.
  • Unlike most taxes that distort incentives and cause deadweight loss (as seen in Ch. 8), corrective taxes actually improve economic efficiency by correcting a market failure.
• Corrective Subsidies: Used for positive externalities (like education). The government pays part of the cost to encourage more of the activity.

Private Solutions to Negative Externalities?

• meaning, make the parties involved feel the costs or benefits of their actions
• Moral Codes and Social Sanctions: Most people don’t litter or cut in line, not because it’s illegal, but because it’s “the right thing to do.” Social pressure forces people to consider how their actions affect others.
• Charities: Non-profits are often established to deal with externalities. For example, the Sierra Club is a private organization that addresses the externality of pollution through private donations.

The Coase Theorem

The Coase theorem states that if property rights are clearly defined and transaction costs are zero, private bargaining between affected parties will lead to an efficient outcome regardless of how property rights were initially assigned.

Example: A factory emitting pollution that harms a nearby laundry. If the laundry has the right to clean air, the factory can pay the laundry to accept some pollution. If the factory has the right to pollute, the laundry can pay the factory to reduce emissions. In either case, bargaining leads to the efficient level of pollution — the same outcome.

Limitations:

• High transaction costs: bargaining breaks down when many parties are involved (coordination costs, free-riding)
• Legal barriers: contracts may be difficult to enforce
• Asymmetric information: parties may not know each other’s true costs or benefits

Despite these limitations, the Coase theorem provides the intellectual foundation for market-based environmental policy.

Tradable Pollution Permits (Cap and Trade)

Instead of directly regulating pollution or taxing it, the government can set a total cap on emissions and issue tradable permits equal to that cap. Firms that can reduce pollution cheaply sell their excess permits; firms facing high abatement costs buy permits rather than cut emissions. The market price for permits ensures that pollution reduction occurs where it is cheapest, achieving the environmental target at minimum cost.

Cap and trade combines the certainty of a quantity limit (the cap) with the efficiency of market pricing. It was successfully used to phase out acid-rain-causing sulfur dioxide emissions in the United States under the Clean Air Act Amendments of 1990.

Public Goods and Common Resources

Excludability: Can people be prevented from using the good?

• Example: A piece of clothing is excludable (you have to pay for it); FM radio signals are not (anyone with a receiver can listen).

Rivalry in Consumption: Does one person’s use of the good diminish another person’s ability to use it?

• Example: If I eat a cheeseburger, you cannot eat that same cheeseburger (Rival). If I watch a sunset, it doesn’t stop you from watching it (Non-rival).

Public Goods Example

• National Defense
• Basic Research
• Fighting Poverty

Common resources face a unique problem because they are:

• Non-excludable: You cannot easily prevent people from using them (e.g., fish in the ocean).
• Rival in Consumption: One person’s use of the resource reduces another person’s ability to use it. If I catch a fish, there is one less fish for you to catch.

Real-World Examples of Common Resources

1. Clean Air and Water: Pollution is a modern version of the tragedy. Firms and individuals treat the environment as a “free” dumping ground, leading to excessive pollution.
2. Congested Roads: If a road is not a toll road (non-excludable) but is crowded (rival), every extra driver creates a delay for everyone else.
3. Fish, Whales, and Other Wildlife: Many species have been hunted to near extinction because the “ocean” is a common resource where it is difficult to enforce property rights.

Free-Rider Problem

A free-rider is a person who receives the benefit of a good but avoids paying for it. Public goods are non-excludable, so people have an incentive to let others pay and enjoy the benefit without contributing. This leads to under-provision by the private market — the classic justification for government provision of public goods.

Lindahl Pricing

Lindahl pricing is a theoretical solution to the free-rider problem. Each individual pays a price (Lindahl tax) equal to their marginal benefit from the public good. If everyone pays their Lindahl price, the sum of individual contributions covers the total cost and the public good is provided at the efficient level. In practice, Lindahl pricing is difficult to implement because individuals have no incentive to reveal their true willingness to pay — they will understate their benefit to reduce their tax burden.

Samuelson Condition

The Samuelson condition states the efficiency rule for public good provision:

$\sum_i MRS_i = MRT$

The sum of the marginal rates of substitution across all consumers (the sum of individuals’ willingness to pay for an additional unit of the public good) must equal the marginal rate of transformation (the marginal cost of producing the public good). For private goods, efficiency requires each individual’s MRS equals the MRT; for public goods, the sum of MRS across all consumers equals the MRT because the good is non-rival — one unit benefits everyone.