Externalities

What Are Externalities and Why Does the Market Ignore Them

Externality (external effect, externality) is the impact of economic activity on third parties who are not direct participants in the transaction and whose interests are not reflected in the market price. This is one of the most common and significant causes of market failure.

Why does the market “not see” externalities? Because market prices are formed based on private costs and benefits — those incurred or received by direct participants in the transaction (buyer and seller). Costs or benefits “spilled over” to third parties are not included in the price and therefore are not considered when making decisions.

Imagine a factory that dumps waste into a river. The pollution costs (deteriorating health of residents, fish kills, loss of the river's recreational value) are borne neither by the factory nor its clients, but by the residents of the surrounding area and fishermen. Since the factory does not pay for these costs, it produces more than is socially efficient, and the price of its products is lower than it would be if full social costs were considered.

Four Types of Externalities

1. Negative Production Externalities

Productive activity creates costs for third parties that are not reflected in the price of the good.

MSC = MPC + MEC (marginal social cost = private + external)

Since MEC > 0, MSC > MPC. The market (based on MPC) produces more than is socially efficient (determined by MSC). The socially optimal output Q* (where MSB = MSC) is less than the market output Q_market (where MSB = MPC).

Examples:

Industrial air pollution. Coal-fired power plants emit sulfur dioxide (SO₂), nitrogen oxides (NOx), and particulate matter, causing respiratory diseases, acid rain, and climate change. According to WHO estimates, air pollution causes about 7 million premature deaths annually worldwide. In China, economic losses from air pollution are estimated at 6–9% of GDP. None of these costs are included in the price of electricity generated by coal-fired plants.

Greenhouse gas emissions and climate change. Burning fossil fuels emits CO₂, which causes global warming. This is arguably the largest negative externality in human history. Nicholas Stern, in his famous 2006 report, estimated the potential damage from climate change at 5–20% of global GDP annually, calling it “the greatest market failure the world has ever seen.”

Traffic congestion. Every additional car on the road slows down all other drivers. The driver considers their own private costs (gasoline, time), but does not consider the time lost by others due to their presence on the road. As a result, roads are overcrowded beyond the socially efficient level.

2. Negative Consumption Externalities

Consumption of a good creates costs for third parties.

MSB = MPB - MEC (in this case, MSB < MPB, because consumption causes harm to third parties)

The market (based on MPB) consumes more than is socially efficient.

Examples:

Smoking. The smoker receives a private benefit (pleasure, stress relief) but creates costs for others: passive smoking increases the risk of lung cancer among non-smokers, higher healthcare costs fall on the mandatory health insurance system (i.e., all taxpayers), productivity declines in the workplace. According to the CDC (USA), the annual economic damage from smoking in the US exceeds $300 billion, including medical costs and lost productivity.

Noise pollution. Nightclubs, construction sites, airports create noise, lowering the quality of life and health of local residents. Studies show that chronic noise increases the risk of cardiovascular disease by 10–20%.

Excessive alcohol consumption. A drunk driver poses a fatal danger to other road users. Domestic violence associated with alcoholism harms families. The costs of treating alcohol dependence fall on the healthcare system.

3. Positive Production Externalities

Production of a good creates benefits for third parties that are not reflected in the price.

MSC = MPC - MEB (social costs are lower than private because production creates secondary benefits)

The market produces less than is socially efficient.

Examples:

Scientific research and development (R&D). When a company invests in basic research, the results often “spill over” to other firms and society as a whole — through publications, patents (which disclose information), employees moving to competitors. Bell Labs research (AT&T’s laboratory) led to the invention of the transistor, the laser, the C and Unix programming languages — technologies that brought benefits far beyond AT&T. Since the firm cannot appropriate all the benefits of its research, it invests in R&D less than would be socially optimal.

Beekeeping near orchards. The beekeeper’s bees pollinate neighboring farmers' trees, increasing their yields. The beekeeper does not receive payment for this, so may keep fewer bees than would be socially efficient.

4. Positive Consumption Externalities

Consumption of a good creates benefits for third parties.

MSB = MPB + MEB (social benefits are greater than private)

The market consumes less than is socially efficient.

Examples:

Education. When a person becomes educated, he/she not only increases his/her own income (private benefit) but also creates many benefits for society: a more educated workforce increases the economy’s productivity, crime rates decline, the quality of civic engagement and democracy improves, and the overall cultural level rises. According to World Bank estimates, each additional year of education in the population increases a country's GDP by 8–13%. Since individuals consider only their private benefit (salary), demand for education in a free market will be below the socially efficient level.

Vaccination. When a person gets vaccinated, he/she protects not only himself/herself but also others — herd immunity arises. If a sufficiently large proportion of the population is vaccinated, the disease cannot spread even among the unvaccinated. The COVID-19 pandemic vividly demonstrated this principle. On a free market, the level of vaccination would be below the socially efficient level because each person considers only his/her private benefit (self-protection), not the benefit to society.

Use of public transport. When a person uses the subway instead of a car, he/she reduces road congestion and pollution for all city residents.

Graphical Analysis: Verbal Explanation

Negative Externality (Overproduction)

Let’s graphically represent the electricity market produced by coal-fired plants.

On the horizontal axis — the quantity of electricity (Q), on the vertical — price/costs (P).

The supply curve reflects private marginal costs (MPC). The demand curve reflects marginal private (and, let's assume, social) benefit (MPB = MSB).

Market equilibrium: intersection of demand and supply gives Q_market and P_market.

However, electricity production creates pollution — a negative externality. The MSC curve lies above MPC by the size of the external cost (MEC). The socially efficient output Q* is determined by the intersection of MSB and MSC. Since MSC > MPC, Q* < Q_market.

Between Q* and Q_market lies the deadweight loss triangle — the area where each additional unit costs society more (MSC) than it brings in benefits (MSB). These units should not have been produced, but the market produces them because it does not consider external costs.

<div style="text-align: center; margin: 20px 0;"> <svg width="100%" style="max-width: 600px;" viewBox="0 0 540 440" xmlns="http://www.w3.org/2000/svg"> <defs> <marker id="m5-arr2" markerWidth="8" markerHeight="6" refX="8" refY="3" orient="auto"> <polygon points="0 0, 8 3, 0 6" fill="#333" /> </marker> </defs> <line x1="60" y1="20" x2="60" y2="390" stroke="#333" stroke-width="1.5" marker-end="url(#m5-arr2)" /> <line x1="60" y1="370" x2="510" y2="370" stroke="#333" stroke-width="1.5" marker-end="url(#m5-arr2)" /> <text x="25" y="200" font-family="sans-serif" font-size="12" fill="#333" transform="rotate(-90, 25, 200)" text-anchor="middle">Price / Cost (&#8381;)</text> <text x="290" y="405" font-family="sans-serif" font-size="12" fill="#333" text-anchor="middle">Quantity (Q)</text> <line x1="60" y1="340" x2="420" y2="100" stroke="#2563eb" stroke-width="2" /> <text x="425" y="100" font-family="sans-serif" font-size="11" fill="#2563eb" font-weight="bold">MPC (S)</text> <line x1="60" y1="280" x2="420" y2="40" stroke="#dc2626" stroke-width="2.5" /> <text x="425" y="42" font-family="sans-serif" font-size="11" fill="#dc2626" font-weight="bold">MSC</text> <path d="M 140,280 L 200,260" stroke="#dc2626" stroke-width="1" stroke-dasharray="3,3" /> <text x="145" y="275" font-family="sans-serif" font-size="9" fill="#dc2626">(MSC = MPC + MEC)</text> <line x1="60" y1="60" x2="460" y2="340" stroke="#16a34a" stroke-width="2" /> <text x="462" y="338" font-family="sans-serif" font-size="11" fill="#16a34a" font-weight="bold">D (MPB)</text> <polygon points="230,178 310,208 310,178" fill="#e11d48" fill-opacity="0.2" /> <polygon points="230,178 230,208 310,208" fill="#e11d48" fill-opacity="0.2" /> <text x="270" y="200" font-family="sans-serif" font-size="9" fill="#e11d48" font-weight="bold">DWL</text> <circle cx="230" cy="178" r="3" fill="#dc2626" /> <line x1="230" y1="178" x2="230" y2="370" stroke="#dc2626" stroke-width="1" stroke-dasharray="5,3" /> <line x1="60" y1="178" x2="230" y2="178" stroke="#dc2626" stroke-width="1" stroke-dasharray="5,3" /> <text x="230" y="388" font-family="sans-serif" font-size="11" fill="#dc2626" text-anchor="middle" font-weight="bold">Q*</text> <text x="54" y="182" font-family="sans-serif" font-size="11" fill="#dc2626" text-anchor="end">P*</text> <circle cx="310" cy="208" r="3" fill="#2563eb" /> <line x1="310" y1="208" x2="310" y2="370" stroke="#2563eb" stroke-width="1" stroke-dasharray="5,3" /> <line x1="60" y1="208" x2="310" y2="208" stroke="#2563eb" stroke-width="1" stroke-dasharray="5,3" /> <text x="310" y="388" font-family="sans-serif" font-size="11" fill="#2563eb" text-anchor="middle" font-weight="bold">Qm</text> <text x="54" y="212" font-family="sans-serif" font-size="11" fill="#2563eb" text-anchor="end">Pm</text> <text x="350" y="160" font-family="sans-serif" font-size="10" fill="#555">Overproduction</text> <path d="M 345,162 L 275,195" stroke="#555" stroke-width="0.8" marker-end="url(#m5-arr2)" /> <text x="270" y="430" font-family="sans-serif" font-size="12" fill="#555" font-style="italic" text-anchor="middle">Fig. 1: Negative Externality</text> </svg> </div>

Positive Externality (Underproduction)

Similarly, in the education market, the MSB curve lies above the MPB (consumers consider only their private benefit). The market establishes equilibrium at Q_market (intersection of MPB and MPC), but the socially efficient output Q* (intersection of MSB and MPC) is higher. The deadweight loss is the triangle between Q_market and Q*, reflecting the lost social benefits from the “missing” education.

<div style="text-align: center; margin: 20px 0;"> <svg width="100%" style="max-width: 600px;" viewBox="0 0 540 440" xmlns="http://www.w3.org/2000/svg"> <defs> <marker id="m5-arr3" markerWidth="8" markerHeight="6" refX="8" refY="3" orient="auto"> <polygon points="0 0, 8 3, 0 6" fill="#333" /> </marker> </defs> <line x1="60" y1="20" x2="60" y2="390" stroke="#333" stroke-width="1.5" marker-end="url(#m5-arr3)" /> <line x1="60" y1="370" x2="510" y2="370" stroke="#333" stroke-width="1.5" marker-end="url(#m5-arr3)" /> <text x="25" y="200" font-family="sans-serif" font-size="12" fill="#333" transform="rotate(-90, 25, 200)" text-anchor="middle">Price / Benefit (&#8381;)</text> <text x="290" y="405" font-family="sans-serif" font-size="12" fill="#333" text-anchor="middle">Quantity (Q)</text> <line x1="60" y1="340" x2="440" y2="80" stroke="#2563eb" stroke-width="2" /> <text x="443" y="78" font-family="sans-serif" font-size="11" fill="#2563eb" font-weight="bold">S (MPC)</text> <line x1="60" y1="60" x2="440" y2="310" stroke="#16a34a" stroke-width="2" /> <text x="443" y="308" font-family="sans-serif" font-size="11" fill="#16a34a" font-weight="bold">MPB (D)</text> <line x1="60" y1="40" x2="440" y2="240" stroke="#9333ea" stroke-width="2.5" /> <text x="443" y="238" font-family="sans-serif" font-size="11" fill="#9333ea" font-weight="bold">MSB</text> <path d="M 350,248 L 400,230" stroke="#9333ea" stroke-width="1" stroke-dasharray="3,3" /> <text x="320" y="260" font-family="sans-serif" font-size="9" fill="#9333ea">(MSB = MPB + MEB)</text> <polygon points="240,208 310,188 310,208" fill="#e11d48" fill-opacity="0.2" /> <polygon points="240,208 240,228 310,208" fill="#e11d48" fill-opacity="0.2" /> <text x="275" y="215" font-family="sans-serif" font-size="9" fill="#e11d48" font-weight="bold">DWL</text> <circle cx="240" cy="228" r="3" fill="#16a34a" /> <line x1="240" y1="228" x2="240" y2="370" stroke="#16a34a" stroke-width="1" stroke-dasharray="5,3" /> <line x1="60" y1="228" x2="240" y2="228" stroke="#16a34a" stroke-width="1" stroke-dasharray="5,3" /> <text x="240" y="388" font-family="sans-serif" font-size="11" fill="#16a34a" text-anchor="middle" font-weight="bold">Qm</text> <text x="54" y="232" font-family="sans-serif" font-size="11" fill="#16a34a" text-anchor="end">Pm</text> <circle cx="310" cy="188" r="3" fill="#9333ea" /> <line x1="310" y1="188" x2="310" y2="370" stroke="#9333ea" stroke-width="1" stroke-dasharray="5,3" /> <line x1="60" y1="188" x2="310" y2="188" stroke="#9333ea" stroke-width="1" stroke-dasharray="5,3" /> <text x="310" y="388" font-family="sans-serif" font-size="11" fill="#9333ea" text-anchor="middle" font-weight="bold">Q*</text> <text x="54" y="192" font-family="sans-serif" font-size="11" fill="#9333ea" text-anchor="end">P*</text> <text x="350" y="280" font-family="sans-serif" font-size="10" fill="#555">Underproduction</text> <path d="M 345,282 L 280,225" stroke="#555" stroke-width="0.8" marker-end="url(#m5-arr3)" /> <text x="270" y="430" font-family="sans-serif" font-size="12" fill="#555" font-style="italic" text-anchor="middle">Fig. 2: Positive Externality</text> </svg> </div>

Methods of Government Intervention

1. Taxes (Tax) — For Negative Externalities

A Pigovian tax (named after economist Arthur Pigou) is a tax equal to the marginal external cost (MEC) at the socially efficient output. The idea is simple: make the producer “internalize” (include in its calculations) external costs.

If the external costs from a ton of CO₂ emissions are $50 (social cost of carbon estimate), then a tax of $50 per ton of CO₂ will force power plants to consider these costs. The price of electricity will rise, consumption will fall, and output will approach a socially efficient level.

Carbon tax in practice. Sweden introduced a carbon tax in 1991 — one of the first in the world. By 2023, the rate reached about $130 per ton of CO₂ — one of the highest in the world. Result: from 1990 to 2020, Sweden’s CO₂ emissions fell by 27% while GDP rose by 78%. This clearly demonstrates that economic growth and emission reductions are compatible.

Excise taxes on tobacco and alcohol are another example of Pigovian taxes. In Russia, the excise tax on a pack of cigarettes makes up a significant portion of the retail price (over 60%). Raising excise taxes leads to reduced consumption, especially among youth and low-income people who are most sensitive to prices.

Advantages of taxes: create an incentive to reduce pollution, generate government revenue, allow firms to independently choose the most efficient way to reduce emissions.

Disadvantages: it is difficult to accurately calculate the size of MEC; the tax may be regressive (disproportionately burdening the poor); political resistance; if the tax is too low, it will not provide a socially efficient outcome.

2. Subsidies — For Positive Externalities

A subsidy is a payment from the government to producers or consumers of a good with a positive externality, equal to the marginal external benefit (MEB). The subsidy reduces the effective price for the consumer, increasing consumption to the socially efficient level.

Subsidies for education. Virtually all countries subsidize education — from free schools to university grants. In Finland, education is free at all levels, including universities, because Finnish society views investment in education as one of the main positive externalities.

Subsidies for renewable energy. Many countries subsidize solar and wind energy to compensate for the positive externality (reducing CO₂ emissions versus fossil fuels). In Germany, the Energiewende program included generous “feed-in tariffs” for producers of renewable energy, leading to the share of renewables in electricity production rising from 6% in 2000 to over 45% by 2023.

Subsidies for vaccination and healthcare. Free vaccination is a subsidy compensating for the positive externality of herd immunity.

3. Direct Regulation (Command and Control)

The government sets standards, restrictions, or bans.

Emission standards. The EU sets maximum emission levels of harmful substances for cars (Euro 1 — Euro 7 standards). Each generation of standards tightens requirements: Euro 6 (2014) requires an 84% reduction in NOx emissions from diesel cars compared to Euro 3 (2000).

Bans. Chlorofluorocarbons (CFCs), which destroy the ozone layer, were banned under the Montreal Protocol of 1987. This is one of the most successful examples of international environmental regulation — the ozone layer is gradually recovering and, according to forecasts, will be fully restored by the 2060s.

Advantages: result is more predictable than with taxation; it is possible to prohibit the most dangerous activities completely.

Disadvantages: regulation does not create incentives to reduce emissions below the established standard; “one rule for all” may be inefficient because the cost of emission reduction differs between firms; high administrative costs for monitoring and enforcement.

4. Tradable Permits / Cap and Trade

The government sets an overall cap on emissions and allocates “emission permits” among firms. Firms which can reduce emissions cheaply sell unused permits to firms for whom reduction is more expensive. This allows the target emission level to be achieved with minimal total costs.

EU Emissions Trading System (EU ETS). Launched in 2005, EU ETS is the world’s largest cap-and-trade system, covering more than 10,000 enterprises in 30 European countries. The system covers about 40% of greenhouse gas emissions in the EU. Since launch, emissions in sectors covered by the EU ETS fell by about 43% (by 2023). The price of a carbon allowance rose from €7 in 2005 to €80–100 in 2022–2023, creating a powerful incentive for decarbonization.

Similar systems operate in China (launched in 2021, the largest in scope), South Korea, California, and a number of other jurisdictions.

Advantages: combines certainty of environmental outcome (fixed limit) with economic efficiency (market allocation of quotas); creates a constant incentive for innovation in emission reduction.

Disadvantages: initial allocation of quotas may be unfair (free allocation by “grandfathering” encourages large polluters); quota price volatility creates uncertainty for business; administrative complexity.

Government Failures

While recognizing market failures, economists must also consider that government intervention can itself be ineffective. Government failure is a situation where government intervention does not improve, but worsens the market outcome.

Information problems. The government may not know the exact size of the externality. If a Pigovian tax is set too high, output will fall below the socially efficient level; if too low, the externality will be only partly eliminated.

Bureaucratic inefficiency. Government agencies may act slowly, spend resources on administration, create excessive regulation, increasing business costs without significant improvement in results.

Regulatory capture. Regulated firms may influence the regulator through lobbying, corruption, or “revolving doors” (employees moving between the regulator and the regulated industry). As a result, regulation may protect the interests of the industry, not society.

Unintended consequences. Any regulation may have unexpected side effects. Strict environmental standards in one country may lead to “carbon leakage” — shifting production to countries with less strict regulation, without reducing global emissions.

Political cycle. Politicians may make decisions focused on short-term electoral gains rather than long-term efficiency. Subsidies, once implemented, are difficult to repeal due to resistance from interest groups.

The Coase Theorem

An alternative view on the problem of externalities was proposed by economist Ronald Coase (Nobel Prize 1991).

The Coase theorem states: if property rights are clearly defined and transaction costs are zero, the parties can arrange among themselves an efficient solution to the externality problem, regardless of the initial distribution of property rights.

Example: a factory pollutes a river, causing a fisherman £1000 in damages. Installing a filter costs £600. If the right to a clean river belongs to the fisherman, the factory will install the filter for £600 (cheaper than paying £1000 in compensation). If the right to pollute belongs to the factory, the fisherman can pay the factory to install the filter (any amount from £600 to £1000 will satisfy both). In both cases, the filter will be installed — the efficient outcome.

However, in practice, the theorem faces serious limitations: transaction costs of negotiation are often high (especially when many parties are affected — millions suffering from air pollution cannot effectively organize to negotiate with factories); property rights are not always clearly defined (who owns clean air?); information asymmetry hampers negotiation.

Nevertheless, the Coase theorem is important because it shows: in some cases, market mechanisms (negotiations between parties) can solve the externality problem without government intervention, and the clear definition of property rights is an important step to an efficient solution.

Summary Comparative Table of Methods to Address Externalities

Understanding externalities and methods of correcting them is one of the central topics of economic policy. How successfully society deals with externalities determines environmental quality, population health, the pace of technological progress, and ultimately, the prosperity of future generations.

Practice Problems

Problem 1: Identifying Externalities

Question: For each case, determine: (1) the type of externality, (2) whether the market quantity is too high or too low.

A. A factory pollutes a river during production
B. Vaccination against an infectious disease
C. Loud music late at night
D. A company actively invests in R&D

Solution:
A. Negative production externality. Pollution is a by-product of production, harming third parties (residents, fishermen). MSC > MPC. The market output of production is too high — the firm does not account for environmental damage in its costs and produces more than the socially optimal level.

B. Positive consumption externality. Vaccination protects not only the vaccinated person but also others (herd immunity). MSB > MPB. The market output of consumption is too low — people consider only their own benefit and do not vaccinate enough.

C. Negative consumption externality. Music consumption harms neighbors (sleep disturbance, stress). MSB < MPB. The market output of consumption is too high — the person does not consider the damage caused to others.

D. Positive production externality. Results of R&D often spread as knowledge spillovers, benefiting other firms and society. MSB > MPB. The market volume of R&D investment is too low — the firm cannot appropriate all the benefits of its discoveries.

Problem 2: Should the Government Always Break Up Monopolies?

Question: Discuss the statement: “Governments should always intervene to break up monopolies.”

Solution:
Arguments FOR intervention:

• Monopolies set P > MC, creating deadweight losses and reducing consumer surplus.
• Lack of competitive pressure may lead to X-inefficiency (wasteful management).
• Consumers suffer from higher prices and less choice.

Arguments AGAINST:

• Natural monopolies (water supply, power grids) have such economies of scale that breaking them up would increase average costs and prices for consumers. Better to regulate than to break up.
• Innovation: Large firms (Apple, Google) invest huge sums in R&D. Schumpeter argued that the prospect of monopoly profits stimulates innovation. Breaking up monopolies may reduce incentives for innovation.
• Economies of scale: A monopolist may have lower average costs than many small competitors, potentially meaning lower prices.
• Government failure: Regulators may be captured by regulated industries (regulatory capture), have incomplete information or act for political reasons.

Conclusion: There is no universal answer. The decision depends on the specific market, existence of economies of scale, potential for innovation, and government’s ability to regulate effectively. For natural monopolies — regulation; for monopolies based on anti-competitive behavior — intervention.