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IB DP Economics Study Notes

2.9.1 Characteristics of Public Goods

Public goods play a fundamental role in economics, distinguishing themselves from other goods in the market due to their unique characteristics: non-excludability and non-rivalry. Understanding these characteristics is paramount for students as they form the bedrock for discussions on government intervention, taxation, and other facets of economic policy.

An image illustrating the characteristics of public goods

Image courtesy of carboncollective


When a good is non-excludable, it implies that once it has been produced and provided, there's no efficient way to prevent someone from consuming or benefiting from it, regardless of whether they have paid for it.

Key Insights:

  • Barrier-Free Access: Simply put, everyone can access and benefit from a non-excludable good. Erecting barriers or preventing certain groups from using the good is either impossible or highly inefficient.
  • The Free Rider Dilemma: The nature of non-excludability leads to the free rider problem. This term refers to individuals or entities who benefit from resources, goods, or services without paying for the cost of the benefit. The crux of the issue is that people might exploit the system by using the good without ever contributing to its financing or upkeep. This highlights the importance of understanding externalities and welfare loss.
  • Public Provisioning: Due to the complications presented by the free rider problem, many non-excludable goods are provided by the state or public entities. This ensures that the good remains accessible to everyone, even if private companies might find its production unprofitable. The role of government in addressing market failures is crucial in this context.
IB Economics Tutor Tip: Grasping public goods' non-excludability and non-rivalry is crucial for understanding why certain services, like defence and street lighting, are typically provided by the government rather than private sectors.

Examples and Elaborations:

1. National Defence: A nation's defence mechanisms, such as its army, navy, and air force, operate to protect all citizens. Even if a resident avoids tax, possibly the primary funding source for defence, they're still shielded by the nation's military. It's impractical to exclude non-contributors from this protection.

2. Street Lighting: The presence of street lights benefits everyone in its vicinity. Once illuminated, it's not feasible to restrict its light only to those who contributed to its funding or maintenance.


A good's non-rival nature means that one individual's consumption doesn't impede or lessen its availability or benefit for another person.

Deep Dive:

  • Simultaneous Consumption: One of the marvels of non-rival goods is their capacity for shared consumption. Multiple individuals can simultaneously benefit from the good without its value diminishing. This is a direct contrast to the definition of externalities, where the impact of one's actions on others is more tangible.
  • Marginal Costs: Economically speaking, the marginal cost of allowing an additional user to consume the good is virtually zero. This means that increasing the number of users doesn't necessarily raise the total costs associated with the good's provision.
  • Constant Availability: Regardless of how many individuals have consumed or benefited from a non-rival good, it remains undiminished and constantly available for others.

Examples and Elaborations:

1. Public Parks: The beauty of a park remains largely undisturbed no matter its visitor count. A thousand people can appreciate a park's scenic beauty, and it would still be as picturesque for the thousand-and-first visitor.

2. Radio and TV Broadcasts: The broadcast of a particular programme doesn't wane in quality or content, regardless of the number of listeners or viewers. This mass, simultaneous consumption doesn't degrade the original content in any manner.

3. Clean Air: While air can be polluted, its natural state is a non-rival good. Every breath taken by an individual doesn't subtract from the air's total volume or make it less available for the next person.

IB Tutor Advice: For exams, relate public goods to real-world examples and discuss their implications on government policy and market failure to demonstrate a deep understanding of economic principles.

Contextual Application

Public goods and their characteristics provide a fascinating study in economic dynamics. They challenge conventional market ideologies, often necessitating government or collective action to ensure optimal provision and maintenance. Students should remain attuned to debates around public goods, especially in contemporary contexts, like digital information or climate stability. The discussion around taxation and subsidies is integral to understanding how governments can intervene to support the provision of public goods.

Moreover, the nuances of public goods also highlight potential market failures. When private entities can't profitably produce these goods due to their non-excludable or non-rival nature, it might lead to underproduction or complete absence in a free market, necessitating public intervention. Thus, understanding these characteristics paves the way for more advanced discussions on market dynamics, government policies, and societal well-being.


Not all public goods are funded or provided by the government. While governments often step in to provide public goods due to the private sector's reluctance stemming from profitability concerns, there are instances where non-governmental organisations, charities, or community groups provide public goods. Examples include community gardens, free open-source software, and certain educational resources. The primary aim in such cases is not profit but the welfare of the community or society at large. These goods are typically funded through donations, philanthropy, or voluntary community efforts.

Technically, public goods cannot be "overconsumed" in the traditional sense, because one person's consumption does not reduce the amount available for another (non-rivalry). However, excessive usage or dependency can strain resources or infrastructure supporting the public good. For example, while a public park is non-rivalrous, excessive visitors might lead to environmental degradation. The implications of such excessive usage include potential degradation of the good itself, increased maintenance costs, and the potential need for regulations or rules to manage and protect the resource for future users.

By definition, public goods are non-excludable. This means that once the good is provided, it's challenging to prevent someone from benefiting from it, even if they haven't paid. If a private company were to find a mechanism to exclude users, the good would no longer retain its status as a 'public' good and would transition closer to a private or quasi-public good. This change in nature would alter the dynamics of consumption and provision, and the company would then face a different set of economic challenges and considerations.

Quasi-public goods share characteristics with both public and private goods, making them somewhat of a hybrid. While they exhibit features of non-excludability and non-rivalry, they don't fully satisfy both conditions. For instance, a toll road can be seen as a quasi-public good. It's non-rivalrous because multiple vehicles can use it simultaneously without diminishing its utility for others. However, with a toll in place, it is somewhat excludable as those who don't pay cannot use it. Contrastingly, a public good fully embodies both non-excludability and non-rivalry, like a public park, where everyone can benefit and one's enjoyment doesn't detract from another's experience.

Measuring the societal value of public goods is challenging due to the absence of market prices, making it difficult to ascertain individuals' willingness to pay. Since public goods are non-excludable and non-rivalrous, consumers often have no incentive to reveal their true valuations, leading to the 'free-rider' issue. Moreover, using surveys or hypothetical scenarios to gauge consumer valuations can introduce biases and inaccuracies. Unlike private goods where demand and price provide clear indicators of value, public goods lack these straightforward metrics, necessitating alternative and often complex valuation methods.

Practice Questions

Describe the characteristics of public goods and explain why they might not be provided in sufficient quantities by the private sector.

Public goods are distinguished by two main characteristics: non-excludability and non-rivalry. Non-excludability means that once the good is provided, it's difficult or inefficient to prevent someone from consuming it, regardless of whether they have contributed to its cost. This leads to the free rider problem, where individuals can benefit without paying. Non-rivalry means that one person's consumption doesn't reduce its availability or benefit for another. The combination of these traits makes it challenging for the private sector to profitably provide these goods. Without the ability to exclude non-payers and without diminished availability due to consumption, the private sector might find it unprofitable to produce and might underprovide or completely abstain from creating such goods.

Using examples, explain the difference between non-excludability and non-rivalry in the context of public goods.

Non-excludability pertains to the inability to prevent individuals from accessing and benefiting from a good once it's provided. For instance, once street lighting is established in a neighbourhood, all residents benefit from it regardless of their contribution. On the other hand, non-rivalry suggests that one person's consumption doesn't reduce the benefit or availability for another person. An example is a radio broadcast; irrespective of how many listeners tune in, the broadcast's quality remains unchanged for every listener. While non-excludability deals with the issue of access, non-rivalry focuses on the undiminished quality or quantity even with multiple consumers.

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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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