Module 6: Environmental and Public Economics¶

Erin Brockovich (2000) Elinor Ostrom

Overview¶

In November 2017, Delhi's air quality index breached 999 — the maximum the monitoring equipment could register. Schools shut, flights were diverted, and hospitals reported a surge in respiratory emergencies. The city's 20 million residents were, in effect, breathing poison. Yet no single factory, vehicle, or construction site had done anything illegal. Each was acting within its private interest. The damage was a collective outcome — an externality — that no market participant had agreed to bear and no market price had accounted for.

This module is about what happens when markets fail to protect shared resources. Markets are extraordinarily powerful at coordinating private production and consumption, as you learned in earlier modules. But they have a blind spot: they ignore costs and benefits that fall on people who are not part of the transaction. A factory pollutes a river because the pollution cost is borne by downstream villagers, not by the factory or its customers. A farmer does not vaccinate her livestock because the disease-prevention benefit accrues to neighboring farms, not to her. These spillover effects — externalities — are among the most important reasons governments intervene in markets.

But government intervention is not the only answer, and it is not always the best one. The most surprising insight in this module comes from Elinor Ostrom, the first woman to win the Nobel Prize in Economics, who spent decades documenting how communities around the world — from Swiss alpine villages to Filipino fishing cooperatives to Uttarakhand's Van Panchayats — successfully govern shared resources without privatization or top-down regulation. Her work offers a third way between the market and the state, and it is deeply relevant to India, where community-managed forests, water systems, and grazing lands have existed for centuries.

We close the course here because environmental economics brings together every concept you have studied: scarcity (of clean air, water, biodiversity), incentives (that drive pollution and conservation), market failure (externalities and public goods), collective action (organizing communities), and policy design (taxes, regulations, and property rights). If you can analyze an environmental problem using the economist's toolkit, you can analyze almost anything.

Key Concepts¶

Externality — a cost or benefit of a transaction that falls on someone not party to it
Negative Externality — an external cost imposed on third parties (e.g., pollution)
Positive Externality — an external benefit enjoyed by third parties (e.g., vaccination)
Public Good — a good that is non-rival and non-excludable (e.g., national defense, clean air)
Private Good — a good that is rival and excludable (e.g., a sandwich, a pair of shoes)
Common Pool Resource — a resource that is rival but non-excludable (e.g., fisheries, forests)
Free Rider — someone who enjoys the benefit of a public good without contributing to its provision
Tragedy of the Commons — the tendency for shared resources to be overused when access is unrestricted
Pigouvian Tax — a tax on activities that generate negative externalities, set equal to the external cost
Carbon Tax — a Pigouvian tax specifically on carbon dioxide emissions
Cap-and-Trade — a system that sets an overall pollution limit and lets firms trade emission permits
Regulation — government rules that directly restrict or mandate behavior
Sustainability — meeting present needs without compromising future generations' ability to meet theirs
Collective Action — coordinated effort by a group to achieve a shared goal
Commons Governance — rules and institutions that communities develop to manage shared resources

Externalities: When Markets Miss the Full Cost¶

An externality occurs when a transaction between two parties imposes costs or benefits on a third party who did not choose to be involved. The market price reflects the private costs and benefits of the buyer and seller, but it ignores these external effects. This means the market produces the wrong quantity: too much of goods with negative externalities, and too little of goods with positive externalities.

Negative Externalities¶

A negative externality is a cost imposed on others. The textbook example is pollution: a factory discharges effluent into a river because it is cheaper than treating the waste. The factory's cost of production is low, so its products are cheap, so consumers buy a lot. But the full cost — including the health damage to downstream communities, the loss of fisheries, the cost of water purification — is much higher than the factory's private cost. The market overproduces because the price does not reflect the true social cost.

Indian Context

Delhi's air pollution crisis is a cascading negative externality. Stubble burning by farmers in Punjab and Haryana (who face no cost for the smoke that drifts southeast), vehicle emissions from 11 million registered vehicles, construction dust, and industrial discharge all contribute. The Economic Survey 2022-23 estimated that air pollution costs India 1.4% of GDP annually in health expenditure and lost productivity. No single polluter bears this cost; it is dispersed across millions of residents in the form of asthma, cardiovascular disease, and shortened lives.

The Bhopal gas tragedy (1984) represents the most catastrophic industrial externality in history. When a pesticide plant owned by Union Carbide leaked methyl isocyanate gas, an estimated 3,800 people died immediately and over 500,000 were exposed. Decades later, groundwater contamination continues to cause birth defects and chronic illness. The settlement of $470 million — roughly $500 per victim — was widely regarded as grossly inadequate, illustrating how markets and legal systems struggle to price catastrophic externalities after the fact.

Positive Externalities¶

A positive externality is a benefit enjoyed by others who are not party to the transaction. When you get vaccinated, you protect not just yourself but everyone you might have infected — the benefit spills over to the community. When a company trains its workers, some of those workers will eventually move to other firms, taking their skills with them — the training benefit spills over to the industry.

Because the private benefit to the decision-maker is less than the total social benefit, the market underproduces goods with positive externalities. Too few people get vaccinated. Firms underinvest in training. Individuals underinvest in education.

Indian Context

India's pulse polio immunization campaign is a textbook positive externality success story. By vaccinating hundreds of millions of children, India achieved polio-free status in 2014. Each vaccination protected not only the child but the entire community through herd immunity. The government subsidized vaccination precisely because the social benefit (disease eradication) far exceeded the private benefit (one child's protection).

Education generates enormous positive externalities. A literate population is more productive, healthier, and more civically engaged. India's Right to Education Act (2009), which guarantees free education to children aged 6-14, is an attempt to push education provision closer to the socially optimal level, recognizing that parents making private decisions underinvest relative to what society needs.

Public Goods: Non-Rival and Non-Excludable¶

A public good has two defining characteristics: it is non-rival (one person's use does not reduce what is available for others) and non-excludable (you cannot prevent anyone from using it). National defense is the classic example: protecting one citizen does not reduce protection for another, and you cannot exclude any resident from its benefits.

Clean air, street lighting, basic scientific research, and lighthouses are all public goods. The problem is obvious: if you cannot exclude non-payers, why would anyone voluntarily pay? This is the free rider problem. Everyone wants clean air, but each individual has an incentive to let others bear the cost of cleaning it up while enjoying the benefits for free. If everyone free rides, the good is not provided at all — or is provided at far less than the optimal level.

This is why governments typically provide public goods, financing them through taxation. The free rider problem makes voluntary provision unreliable.

Indian Context

The Ganga cleanup illustrates the public goods problem on an epic scale. The Namami Gange programme, launched in 2014 with a budget exceeding Rs 30,000 crore, aims to clean India's holiest and most polluted river. A clean Ganga is a public good — non-rival and non-excludable. But the costs of cleanup fall on taxpayers, while the polluters (industries, cities, and agricultural runoff from five states) have limited incentive to reduce their discharge. The programme has struggled precisely because the benefits are diffuse and long-term while the costs of reducing pollution are concentrated and immediate.

The Classification Matrix¶

Not all goods are purely private or purely public. Economists classify goods along two dimensions:

	Excludable	Non-Excludable
Rival	Private good (food, clothing)	Common pool resource (fisheries, forests)
Non-Rival	Club good (streaming service, toll road)	Public good (national defense, clean air)

The most interesting — and most troubled — quadrant is the lower-left cell: common pool resources. These are rival (one person's use reduces what is available for others) but non-excludable (it is difficult to prevent access). Fisheries, groundwater, forests, and grazing lands all fit this category. And they are the setting for one of the most famous and most debated ideas in economics.

The Tragedy of the Commons¶

In 1968, biologist Garrett Hardin published an influential essay arguing that shared resources are doomed to depletion. His reasoning was simple: if a pasture is open to all herders, each herder has an incentive to add one more animal. The benefit of that additional animal goes entirely to the herder, while the cost of overgrazing is shared among all. Each herder reasons identically, and the pasture is destroyed. This is the Tragedy of the Commons.

Hardin's argument was powerful and had enormous policy influence. If shared resources inevitably collapse, then the solutions are clear: either privatize the resource (give each herder a private plot) or have the government regulate access (limit the number of animals). For decades, these were seen as the only two options.

Indian Context

India's groundwater crisis is a real-world tragedy of the commons. India is the world's largest user of groundwater, extracting roughly 25% of the global total. With over 30 million tube wells and minimal regulation, each farmer has an incentive to pump as much as possible before their neighbor does. The Central Ground Water Board classifies 17% of India's assessment units as "over-exploited." In Punjab, where the Green Revolution drove a massive expansion of wheat and rice cultivation, the water table has been falling by nearly one meter per year in some districts. The resource is rival (water pumped by one farmer is unavailable to another) and effectively non-excludable (enforcement of extraction limits is nearly impossible with millions of small users).

India's fisheries tell a similar story. Marine fish stocks along the Kerala and Tamil Nadu coasts have declined dramatically as motorized trawlers compete with traditional fishing communities for dwindling stocks. The ocean is a common pool resource, and without effective governance, the race to fish threatens both the resource and the livelihoods that depend on it.

Policy Solutions: Fixing Market Failure¶

When externalities and public goods problems cause markets to fail, economists have identified several policy tools to bridge the gap between private costs and social costs.

Pigouvian Taxes¶

Named after British economist Arthur Pigou, a Pigouvian tax is levied on activities that generate negative externalities, ideally set equal to the external cost per unit. If a factory's pollution causes Rs 100 in damage per ton of output, a Pigouvian tax of Rs 100 per ton forces the factory to internalize the external cost. The market price rises, quantity falls, and production moves closer to the socially optimal level.

The beauty of a Pigouvian tax is that it uses the price mechanism rather than fighting it. The factory is not told how to reduce pollution — it might install filters, switch to cleaner inputs, or reduce output. The tax simply ensures the pollution cost is borne by the polluter, and the market finds the cheapest way to respond.

A carbon tax is the most discussed Pigouvian tax today. By pricing each ton of carbon dioxide emissions, a carbon tax gives every firm and household an incentive to reduce their carbon footprint — but leaves the method entirely to them.

Cap-and-Trade¶

An alternative market-based mechanism is cap-and-trade. The government sets an overall cap on total emissions, then issues permits (each allowing a certain amount of pollution) and allows firms to trade them. Firms that can reduce emissions cheaply sell their excess permits to firms that find it more expensive to cut. The result: the same total reduction, achieved at the lowest possible cost, because reductions happen where they are cheapest.

Indian Context

India launched its carbon credit trading scheme in 2023, making it one of the first developing countries to establish a formal domestic carbon market. The scheme, administered under the Energy Conservation (Amendment) Act 2022, sets emission intensity targets for heavy industries and allows trading of Carbon Credit Certificates. It draws directly on cap-and-trade principles, adapted to India's context of energy-intensive industrialization.

India's Perform, Achieve, and Trade (PAT) scheme, operational since 2012, is effectively a cap-and-trade system for energy efficiency. It covers over 1,000 energy-intensive industrial units across 13 sectors. Plants that exceed their efficiency targets earn Energy Saving Certificates that can be sold to plants that fall short. By 2023, the scheme had achieved cumulative energy savings of over 26 million tonnes of oil equivalent.

Regulation¶

Sometimes the simplest solution is direct regulation: ban the pollutant, mandate a technology, or set an emission standard. India's shift from BS-IV to BS-VI emission standards for vehicles in 2020 — skipping BS-V entirely — was a regulatory mandate that forced automakers to adopt cleaner technology. The Supreme Court's ban on firecrackers in Delhi during Diwali is another example of command-and-control regulation.

Regulation is straightforward but has limitations. It does not allow firms to find the cheapest way to reduce pollution (a blanket standard treats all firms the same, regardless of their abatement costs). And it requires enforcement — a persistent challenge in India, where regulatory capacity often lags behind regulatory ambition.

Property Rights: The Coase Theorem¶

Economist Ronald Coase argued in 1960 that if property rights are clearly defined and transaction costs are low, private bargaining can resolve externalities without government intervention. If a factory has the legal right to pollute, the downstream village could pay the factory to reduce emissions — if the damage exceeds the factory's cost of abatement, both sides gain from the deal. If the village has the right to clean water, the factory pays the village for permission to pollute.

In theory, the outcome is efficient regardless of who holds the initial right. In practice, the Coase theorem is limited by high transaction costs, power asymmetries, and the difficulty of organizing large groups of affected parties — exactly the conditions that characterize most environmental problems.

Ostrom's Alternative: Communities Can Govern the Commons¶

For decades, the economics of shared resources was dominated by a binary: privatize or regulate. Then Elinor Ostrom changed the conversation.

Through painstaking fieldwork studying irrigation systems in Nepal, fisheries in Turkey and Sri Lanka, forests in Japan and India, and pastures in Switzerland and Kenya, Ostrom documented hundreds of cases where communities had successfully governed common pool resources for centuries — without privatization and without government control. She identified eight design principles that characterized successful commons governance:

Clear boundaries — who can use the resource and who cannot
Rules matched to local conditions — not one-size-fits-all
Collective choice — users participate in making the rules
Monitoring — by users themselves or by accountable agents
Graduated sanctions — penalties that start mild and escalate
Conflict resolution — accessible, low-cost mechanisms
Autonomy — external authorities recognize the community's right to organize
Nested enterprises — for large systems, governance is layered from local to regional

Indian Context

Van Panchayats of Uttarakhand are among the world's oldest community forest governance systems, predating Ostrom's research but validating her theory with remarkable precision. Established under the Van Panchayat Rules of 1931, these community-managed forests cover over 500,000 hectares across roughly 12,000 villages. Each Van Panchayat sets its own rules about harvesting timber, collecting non-timber forest products, and grazing — with monitoring by community members and graduated penalties for violations. Research by Agrawal and Ostrom (2001) found that Van Panchayat forests in Kumaon showed better ecological outcomes than both state-managed forests and open-access areas.

Rajasthan's johad revival is another Ostrom-compatible success story. In the 1980s, Rajendra Singh and the Tarun Bharat Sangh began reviving traditional water harvesting structures (johads) in Alwar district. By organizing village communities to collectively maintain these earthen dams, the initiative recharged groundwater, revived five rivers, and transformed barren landscapes into productive farmland. The key was collective action governed by local rules — precisely the institutional arrangement Ostrom described.

Kerala's fishing communities have traditionally governed marine commons through informal institutions. Village-level koodams (assemblies) regulate fishing seasons, gear types, and entry into fishing grounds. These systems have operated for generations, demonstrating that communities can manage complex, mobile resources like fish stocks when they have the institutional capacity to monitor and enforce rules.

Sustainability and Climate Economics¶

All the concepts in this module converge on the defining challenge of the twenty-first century: climate change. Carbon emissions are a negative externality on a planetary scale. The atmosphere is a global commons. Climate stability is a public good. And the nations of the world face a collective action problem of staggering complexity.

Sustainability — meeting present needs without compromising future generations' ability to meet theirs — requires thinking about externalities, commons, and collective action across time. The decisions we make today about energy, land use, and consumption impose costs on people who have not yet been born and therefore cannot participate in today's markets. This is the deepest market failure of all: the market has no mechanism for representing the interests of the future.

Indian Context

India occupies a unique position in climate economics. As the world's third-largest emitter of greenhouse gases but also one of the most climate-vulnerable nations, India faces the tension between development and sustainability more acutely than any other large economy. Per capita emissions remain well below the global average — roughly one-third of China's and one-eighth of the United States' — yet the absolute scale of India's economy means that its emission trajectory shapes the global outcome.

India's International Solar Alliance (ISA), co-founded with France in 2015, is a collective action solution to a global commons problem. By bringing together over 110 countries to scale up solar energy deployment, the ISA addresses the free rider problem in climate mitigation: no single country has sufficient incentive to invest in clean energy alone, but coordinated action can drive down costs for everyone. India's own solar capacity has grown from under 3 GW in 2014 to over 70 GW by 2023.

The Chipko movement of the 1970s, in which women in Uttarakhand's Garhwal hills physically embraced trees to prevent logging by commercial contractors, is one of the earliest examples of grassroots environmental collective action. The movement — which literally means "to cling" — combined environmental protection with community rights over forest resources. It influenced India's Forest Conservation Act of 1980 and inspired environmental movements worldwide. In the language of this module, Chipko was collective action to protect a common pool resource from an externality imposed by commercial extraction.

Connecting to the Film¶

Scene Connection: Erin Brockovich (2000)

In Erin Brockovich, a small-town legal clerk discovers that Pacific Gas & Electric has been poisoning the groundwater of Hinkley, California, with hexavalent chromium — a carcinogenic industrial waste. The company knew about the contamination but concealed it, and the residents suffered cancers, miscarriages, and chronic illness for decades without understanding why. The film is a case study in negative externalities, information asymmetry, regulatory failure, and the power of collective action when institutions fail.

Read the full film analysis

Connecting to the Nobel Laureate¶

Nobel Connection: Elinor Ostrom (2009)

Elinor Ostrom was the first woman to receive the Nobel Prize in Economics — and she was not even an economist by training. A political scientist by education, she spent decades doing what most economists did not: traveling to communities around the world and studying how they actually managed shared resources. Her finding — that communities can and do govern commons successfully through self-organization — overturned the "privatize or regulate" orthodoxy and opened an entirely new field of institutional analysis. Her work resonates powerfully in India, where community governance of forests, water, and fisheries has a history stretching back centuries.

Read the Nobel Focus

Interactive Explorations¶

Try these browser-based simulations to see the module's concepts in action:

Simulation	What to Try	Link
Negative Externality Visualizer	See how pollution causes the market to overproduce beyond the social optimum	Open
Public Goods Game	Experience the free rider problem: will you contribute or let others pay?	Open
Tragedy of the Commons	Watch a shared resource collapse as each user acts in self-interest	Open
Tax Incidence Explorer	Adjust elasticities and see how the burden of a Pigouvian tax shifts between buyers and sellers	Open
Policy Claim Evaluator	Test the logic behind common claims about environmental and tax policy	Open
Feedback Loops	Visualize how environmental degradation can create self-reinforcing cycles	Open

Simulations from Introduction to Economics by Dan McCreary (CC BY-NC-SA 4.0)

Key Takeaways¶

Externalities are costs or benefits that fall on people not party to a transaction — they cause markets to produce the wrong quantity.
Negative externalities (pollution, congestion) lead to overproduction; positive externalities (education, vaccination) lead to underproduction.
Public goods are non-rival and non-excludable — the free rider problem makes private provision inadequate.
Common pool resources are rival but non-excludable — they are vulnerable to the Tragedy of the Commons.
Pigouvian taxes correct externalities by making polluters pay the social cost — using the price mechanism rather than fighting it.
Cap-and-trade sets an overall pollution limit and lets the market find the cheapest way to achieve it.
Regulation (emission standards, bans) is direct but inflexible — it works best when the externality is severe and measurement is straightforward.
Elinor Ostrom showed that communities can govern commons successfully through self-organization — neither privatization nor government control is the only option.
Sustainability requires accounting for externalities across time — the market cannot represent the interests of future generations.
Climate change is the largest collective action problem humanity has ever faced — it combines global externalities, public goods, and commons governance at planetary scale.

Think Like an Economist¶

Reflection Prompts

Identify a negative externality you encounter in your daily life. Who bears the cost? Why does the market fail to account for it? What policy could address it?
India's groundwater is a classic common pool resource. Using Ostrom's eight design principles, evaluate why community governance has succeeded in some Indian states (Rajasthan's johads) but not others (Punjab's tube wells). What institutional differences explain the divergent outcomes?
A carbon tax makes fossil fuels more expensive, which disproportionately affects lower-income households who spend a larger share of their income on energy. Does this mean India should not implement a carbon tax? How might you design the policy to address this equity concern?

Where to Go From Here¶

You have now completed all six modules of this course. You began with the foundational ideas of scarcity, opportunity cost, and trade-offs. You explored incentives and strategic behavior. You analyzed markets, labor, poverty, inequality, innovation, and growth. And you have ended here, with the recognition that markets — for all their power — have systematic blind spots when it comes to the environment, shared resources, and the future.

The economist's toolkit you have built is not a set of answers. It is a set of questions: What are the trade-offs? Who bears the costs? What incentives are driving behavior? Are the institutions well-designed? These questions apply to every policy debate you will encounter — from Delhi's air pollution to global climate negotiations, from local water management to international trade agreements.

Economics is not about memorizing models. It is about seeing the world clearly — with its trade-offs, its incentive structures, its winners and losers — and asking what we can do better. That is a skill that will serve you far beyond this course.

Test yourself: Take the Module 6 Quiz | Explore further: Module 6 Resources