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IB DP Economics Study Notes

2.8.5 Negative Externalities of Consumption

Externalities arise when the consumption or production decisions of one party indirectly influence the well-being of non-consenting third parties. Negative externalities of consumption occur when the consumption of certain goods or services by individuals or firms results in unintended negative consequences for others. For a broader understanding of externalities, see the definition of externalities.


Overconsumption signifies the excessive consumption of goods or services, surpassing what is deemed socially or economically optimal. This phenomenon is typically driven by the misalignment between private and social benefits and costs.

Key Points:

  • Private Benefit: Refers to the direct benefits received by individuals or entities from their own consumption. This is often driven by personal preferences, needs, or circumstances.
  • Social Benefit: Encompasses both the private benefits derived by individual consumers and the benefits (or detriments) experienced by third parties. It reflects the overall impact of consumption on society at large.
  • When the marginal private benefit of consumption exceeds the marginal private cost but fails to account for the negative impact on third parties (external costs), overconsumption arises. Essentially, people consume more than what's socially optimal. The consequences of this misalignment are further explored in the discussion on externalities and welfare loss.
A graph of negative consumption externality

A graph illustrating overconsumption due to negative consumption externality.

Image courtesy of thecuriouseconomist

Effects on Third Parties

The repercussions of negative externalities from consumption touch a broad spectrum of areas and individuals.

1. Health Implications

  • Tobacco Consumption: While smokers face health risks, passive smoking poses threats to non-smokers, resulting in respiratory complications or other related diseases.
  • Junk Food and Obesity: Overconsumption of unhealthy food escalates health costs not just for consumers, but the entire health system which might be publicly funded.

2. Environmental Impact

  • Plastic Usage: Overconsumption of plastics, especially single-use plastics, intensifies environmental pollution. Marine life can mistake plastics for food, leading to fatalities, and water sources can become polluted.
  • Vehicle Emissions: Over-reliance on automobiles contributes to air pollution, affecting not just the drivers but everyone breathing the air.

3. Societal Disruptions

  • Alcohol: Beyond potential health issues, excessive alcohol consumption can be linked to societal problems such as public disturbances or increased crime rates.
  • Noise Pollution: Overuse of loud machinery or tools, especially in densely populated areas, can disturb others, affecting their quality of life.
An infographic illustrating the effect of mandatory label warnings

Image courtesy of healthyfoodamerica

4. Economic Ramifications

  • Depletion of Common Resources: Overfishing, for instance, reduces fish stocks, affecting future fishermen and consumers. This depletion is a specific type of negative externality, similar to those negative externalities of production that also have significant economic impacts.
IB Economics Tutor Tip: Understand the distinction between private and social costs to grasp how overconsumption driven by personal benefit can lead to wider societal and environmental issues.

Corrective Measures

Governments, recognising the misalignment of private and societal costs, might intervene to guide consumption patterns towards more socially optimal levels.

1. Taxes

  • Pigouvian Taxes: Named after economist Arthur Pigou, these are taxes imposed on goods with negative externalities. By increasing the price, it seeks to bring the private cost in line with the social cost. Implementing such taxation strategies is a common approach to addressing the issue.

2. Direct Regulations

  • Quantity Controls: Limit the quantity of a particular good that can be consumed or produced.
  • Bans: Outright bans, like those on certain harmful drugs or products, can curb consumption entirely.

3. Informational Campaigns

  • Awareness Drives: Governments or organisations can launch drives that highlight the adverse effects of overconsumption, persuading individuals to change their behaviour.
  • Labelling: Mandatory labels warning of the adverse effects can deter overconsumption.

4. Subsidies for Alternatives

  • Promoting Healthier Choices: Subsidies on organic or health foods might shift consumption away from unhealthy alternatives. The role of subsidies in promoting positive consumption habits is crucial for public health and environmental sustainability.
  • Encouraging Sustainable Consumption: Financial incentives for using renewable energy sources can make them more attractive relative to non-renewable sources.

5. Tradable Allowance Systems

  • Cap and Trade: Firms are given emission allowances. Those producing less pollution can sell their extra allowances to higher polluters, incentivising overall reduction.

6. Establishing Property Rights

  • Coase Theorem: This theory postulates that clear property rights and low transaction costs enable affected parties to negotiate and potentially resolve externality issues amongst themselves.

7. Government-Provided Public Goods

  • Clean Public Spaces: By providing and maintaining parks or beaches, governments can offer alternatives to privately-consumed goods, potentially reducing overconsumption.

8. Research and Development

  • Innovation: Governments can fund research into sustainable or alternative technologies that reduce the negative externalities of consumption.
IB Tutor Advice: When revising, focus on real-world examples of negative externalities, such as sugar taxes and emission standards, to illustrate how theory translates into practice and policy interventions.

Applications and Examples

  • Sugar Tax: Implemented in various countries, this tax on sugary drinks aims to reduce consumption and associated health issues.
  • Emission Standards: Many countries have stringent emission standards for vehicles, aiming to reduce the negative externalities associated with vehicle emissions.
  • Plastic Bag Levies: By imposing a cost on single-use plastic bags, countries aim to reduce their consumption and the associated environmental externalities.
An image illustrating the plastic bad restrictions in Kirkland

Image courtesy of kpcw

In understanding negative externalities of consumption, the challenge is to reconcile individual freedoms and choices with broader societal well-being. Effective policies can help ensure that the true costs of consumption, including those borne by third parties, are considered in individual consumption decisions.


Absolutely! Raising consumer awareness and educating them about the broader impacts of their consumption choices can lead to more informed decisions. By understanding the external costs associated with certain products or services, consumers might be more inclined to reduce their consumption or switch to more sustainable alternatives. Campaigns highlighting the environmental impact of single-use plastics, for instance, have driven many consumers to adopt reusable bags and containers. While education and awareness are not silver bullets and might not eliminate negative externalities entirely, they can significantly mitigate their severity.

While many negative externalities have long-term harmful effects, not all necessarily persist indefinitely. Some might be short-lived or might get mitigated as society adapts or finds solutions. For instance, the introduction of a new noisy machinery in a neighbourhood might be a negative externality for residents initially. However, over time, the manufacturer might develop quieter versions, or the community might invest in soundproofing. That said, it's crucial to address negative externalities early on, as some, especially environmental ones, can have irreversible long-term consequences if left unchecked.

Government intervention to correct negative externalities, while beneficial in theory, can face numerous challenges in practice. Firstly, accurately measuring the external cost is often difficult, which can lead to under or over-regulation. Secondly, there might be political or economic pressures, including lobbying by powerful industries, that resist regulatory changes. Additionally, there's the risk of unintended consequences. For instance, imposing high taxes on alcoholic beverages might spawn illegal markets. Lastly, there might be a broader philosophical or policy stance favouring free markets and minimal government intervention. Thus, while governments possess tools to address negative externalities, multiple factors influence their application.

The tragedy of the commons describes a situation where individuals, acting in their self-interest, overuse or degrade a shared resource, leading to its depletion or damage. This is closely related to negative externalities of consumption, as in both cases, individual actions lead to adverse effects on the broader community. A real-world example might be overfishing in international waters. Individual fishermen have a private incentive to catch as many fish as possible, but this overconsumption can deplete fish stocks, damaging the ecosystem and hurting all fishermen in the long run. Thus, both concepts highlight the challenges of coordinating individual actions to achieve broader societal benefits.

When consumers make purchasing decisions, they typically consider their private benefits and costs, which directly affect them. External costs, on the other hand, impact third parties rather than the consumers themselves. Many times, consumers might be unaware of these external costs or may undervalue them, leading to overconsumption. For instance, a person might choose to buy a gas-guzzling car, focusing on its power and prestige, without considering the environmental damage from increased CO2 emissions. Additionally, the lack of proper information, understanding, or internalisation of these externalities can lead to such myopic consumption choices.

Practice Questions

Explain how overconsumption of a product can lead to negative externalities, giving a real-world example.

Overconsumption of a product occurs when individuals consume more than the socially optimal level, often because the private benefits they perceive exceed their private costs, disregarding the external costs borne by third parties. A classic real-world example is the overconsumption of cigarettes. While smokers derive a private benefit (pleasure, stress relief) from smoking, they often ignore or undervalue the external costs, such as health problems from passive smoking inflicted on non-smokers. Consequently, the societal cost, encompassing both private and external costs, is greater than the societal benefit, leading to a deadweight loss in welfare.

Discuss one corrective measure a government might implement to address the negative externalities of consumption, illustrating its potential effectiveness.

A common corrective measure employed by governments is the imposition of Pigouvian taxes on goods with negative externalities. By levying a tax equivalent to the external cost, the private cost to consumers increases, thus realigning it closer to the true societal cost. For example, governments might impose higher duties on alcoholic beverages to curtail excessive drinking. The increased price would ideally deter overconsumption, reducing alcohol-related issues like public disturbances or health complications. By bridging the gap between private and social costs, such a tax can guide consumption towards a more socially optimal level, restoring equilibrium and mitigating the negative impacts on third parties.

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Written by: Dave
Cambridge University - BA Hons Economics

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