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IB DP Economics Study Notes

2.8.6 Positive Externalities

Positive externalities refer to the beneficial side effects or consequences of an individual or firm's actions on unrelated third parties. These benefits arise unintentionally from an activity and enhance societal well-being without the beneficiaries having to pay for them directly.

Benefits to Third Parties

The implications of positive externalities are broad and have ripple effects across sectors and industries, increasing the quality of life or well-being for those who did not participate in the initial activity.


Health-based positive externalities arise when individual actions inadvertently lead to collective well-being.

  • Vaccination: When a significant portion of the population gets vaccinated, it becomes difficult for a disease to spread, creating a protective effect for everyone, including those unvaccinated. This phenomenon is termed herd immunity.
  • Health Screenings: Early detection through regular health checks can reduce the spread of contagious diseases, benefiting the wider community.


Educational investments can uplift not only individuals but also the entire community.

  • Skill Acquisition: As individuals become educated, they contribute to a more skilled workforce. This can increase a region's competitiveness, potentially attracting businesses and fostering innovation.
  • Civic Participation: Educated individuals are more likely to participate in civic duties like voting, leading to better governance.
An infographic illustrating positive externality of education

Image courtesy of research


Actions aimed at environmental preservation can have significant positive spillovers.

  • Green Technologies: Companies adopting sustainable practices might reduce environmental degradation, ensuring cleaner surroundings for everyone.
  • Tree Planting: Beyond just the aesthetic appeal, trees absorb carbon dioxide, release oxygen, and provide shade, benefiting all nearby residents.

Under-allocation of Resources

When market participants don't account for the external benefits of their actions, it can lead to inefficient outcomes.

Private vs Social Benefits

  • Private Benefit: Refers to the advantages reaped directly by the parties involved in a transaction.
  • Social Benefit: Encompasses both the direct benefit to involved parties and the indirect benefits to external entities.

In scenarios with pronounced positive externalities, the total societal benefit surpasses the personal gains recognised by the active parties. But the market, left on its own, will typically only account for the private benefits, causing a suboptimal level of production or consumption.

Deadweight Welfare Loss

  • This represents the lost societal well-being due to the under-provision of a product or service with positive externalities. Essentially, it's the welfare that could've been achieved minus the welfare that is achieved.
A graph of positive production externality

A graph illustrating underproduction due to positive production externality.

Image courtesy of thecuriouseconomist

A graph of positive consumption externality

A graph illustrating underconsumption due to positive consumption externality.

Image courtesy of thecuriouseconomist

Encouragement Policies

Addressing the inefficiencies caused by positive externalities requires strategic interventions.


  • Rationale: By financially supporting activities with pronounced external benefits, authorities can stimulate increased production or consumption, moving closer to the socially optimal level.
  • Example: Promoting solar panels by offering rebates can boost their adoption, leading to cleaner energy production.

Regulation and Legislation

  • Mandates: Making certain beneficial actions obligatory, like seat belts in cars, can ensure more people benefit from the positive externalities.
  • Standards: Mandating efficiency metrics, such as minimum mileage for cars, can drive production towards more beneficial products.

Public Provision

Sometimes, the inefficiency is so pronounced that direct intervention becomes necessary.

  • Governments can take on the role of provider to ensure that the societal benefits of certain goods or services are realised. Examples include:
    • Publicly funded schools
    • State-sponsored healthcare

Awareness and Information Campaigns

  • Information Dissemination: Many times, awareness can be a game-changer. Educating the public about the broader benefits of specific actions can encourage more individuals to partake in them.
    • Anti-smoking campaigns
    • Promotions about water conservation

Indirect Encouragements

  • Research Grants: Funding research in areas with high potential for positive externalities, like renewable energy or medicine, can lead to breakthroughs that benefit society.
  • Tax Benefits: Providing tax breaks for firms or individuals undertaking activities with positive spillovers can act as a strong incentive.

Understanding positive externalities is vital for students as it offers insight into market imperfections and showcases the tools at the disposal of policymakers to correct them. Through strategic interventions, societies can harness the full potential of these incidental benefits and craft a more equitable, prosperous landscape for all its members.


Positive externalities and public goods are interrelated but distinct concepts. Both deal with benefits that spill over to others. Goods with positive externalities deliver additional benefits beyond those to the immediate consumer, but they can still be private, excludable goods. Public goods, on the other hand, are inherently non-excludable and non-rivalrous, meaning individuals cannot be easily prevented from using them, and one person's use doesn't reduce availability for others. While many public goods can generate positive externalities (like a public park improving community health), not all goods with positive externalities are public goods.

Absolutely. Positive externalities can arise from both goods and services. For instance, education is a service that provides personal benefits to students in terms of knowledge and potentially better job prospects. However, an educated populace also benefits society as a whole by promoting informed civic participation, fostering innovation, and reducing crime rates. Similarly, a cleaning service for a river doesn't just benefit the immediate area but enhances the environment for the broader community and ecosystems. The key factor is not the physical nature of the good or service, but the spill-over benefits it provides to others.

While positive externalities are generally seen as beneficial, there can be situations where they inadvertently harm certain stakeholders. Consider a scenario where a government recognises the positive externalities of a particular good and heavily subsidises it to promote consumption. This could lead to producers of alternative, non-subsidised goods facing reduced demand and potential financial hardship. Or, in the case of green energy: as governments support and incentivise renewable energy due to its positive externalities, traditional fossil fuel industries might face job losses and economic downturns.

Goods with positive externalities often deliver benefits beyond those reaped by the immediate buyer or user. Because these extra societal benefits don't directly translate into profits for the producers or savings for the consumers, there's less market incentive to produce or consume them in adequate amounts. For instance, a vaccine provides personal health benefits to the one vaccinated, but it also benefits the community by reducing the spread of disease. If a market only focuses on individual benefits, and not on the broader societal benefits, the result could be suboptimal production and consumption of such goods.

Yes, while government intervention, like subsidies, can help address the under-allocation of resources for goods with positive externalities, sole reliance on such measures can introduce inefficiencies. Governments may lack the precise data to set subsidies at the exact needed level, leading to over-compensation or inadequate support. This can distort market signals further. Moreover, there's a risk of political factors influencing the decision-making process, rather than purely economic rationale. Overreliance on government interventions can also stifle private sector innovation in finding solutions to harness the benefits of positive externalities. It's often a balanced approach, considering both market and state roles, that proves most effective.

Practice Questions

Explain how the under-allocation of resources in relation to goods with positive externalities can lead to deadweight welfare loss.

Goods with positive externalities provide additional benefits to society beyond the private benefits enjoyed by individual consumers. When the market only accounts for these private benefits, it tends to produce less than the socially optimal quantity of these goods. This under-allocation results in fewer goods being produced and consumed than what would maximise societal welfare. The difference between the maximum societal welfare possible and the actual welfare achieved is termed deadweight welfare loss. It signifies the lost societal benefits from not fully realising the potential of goods with positive externalities.

Evaluate the effectiveness of subsidies as a policy to address the issue of under-consumption of goods with positive externalities.

Subsidies can effectively increase the consumption of goods with positive externalities. By decreasing the price paid by consumers or increasing the rewards for producers, subsidies make such goods more attractive, leading to higher consumption and production. In doing so, they help bridge the gap between private and social benefits, pushing the market closer to the socially optimal level. However, the success of subsidies depends on correct implementation. They must be set at an appropriate level to prevent over-compensation, and governments must have accurate data to determine this. Additionally, funding the subsidy without causing other inefficiencies in the economy is crucial.

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Written by: Dave
Cambridge University - BA Hons Economics

Dave is a Cambridge Economics graduate with over 8 years of tutoring expertise in Economics & Business Studies. He crafts resources for A-Level, IB, & GCSE and excels at enhancing students' understanding & confidence in these subjects.

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