Business Economics · Public Finance

Public Goods vs Private Goods: CA Foundation Business Economics

Updated 1 October 2026 · Fact-checked

A public good is non-rival and non-excludable: one person's use does not reduce what others get, and nobody can be kept out. A private good is rival and excludable. Classify any good with two tests, rivalry and excludability. The free rider problem arises because people enjoy public goods without paying.

Understand Public Goods vs Private Goods

Every good can be sorted using two questions. First, rivalry: if I consume it, does less remain for you? Second, excludability: can the seller stop you from using it unless you pay?

A private good is rival and excludable. A packet of biscuits is a standard example. If you eat it, I cannot. The shopkeeper will not hand it over until you pay. Markets work well for private goods because price decides who gets them.

A public good is non-rival and non-excludable. National defence, street lighting and lighthouses are standard examples. When one more person is protected by the army, protection for others does not fall. And you cannot protect only those who pay. So private firms find it hard to earn revenue, and the market tends to under-supply or not supply these goods. This is why governments provide them, funded by taxes.

This leads to the free rider problem. A free rider enjoys the benefit of a good without paying for it. If everyone reasons this way, no one pays, the seller earns nothing, and the good is not produced privately. Compulsory taxation solves this because payment is not voluntary.

Two in-between cases also appear. A club good is non-rival (up to a point) but excludable, such as a cable TV subscription or a toll expressway with free-flowing traffic. A common resource (common pool good) is rival but non-excludable, such as fish in the open sea or a public grazing land. Common resources tend to be overused, which is the "tragedy of the commons".

Key formulas to remember

Private good: Rival + Excludable; Example: food, clothes, a mobile phone. Markets supply these efficiently.
Public good (pure): Non-rival + Non-excludable; Example: national defence, street lights, public park with open access. Prone to free riding.
Club good: Non-rival + Excludable; Example: cable TV, a private club, toll road when uncongested. Access can be charged for.
Common resource: Rival + Non-excludable; Example: ocean fish, open grazing land. Prone to overuse.
Free rider problem: Benefit received without paying, because exclusion is not possible; Leads to under-provision of public goods by the market.

How to solve Public Goods vs Private Goods questions

Use the same two-question test on any classification or definition question.

1Read the good or situation described in the question.
2Ask: if one person uses it, is less left for others? If yes, it is rival. If no, it is non-rival.
3Ask: can a person be stopped from using it if they do not pay? If yes, it is excludable. If no, it is non-excludable.
4Match the pair to the four types: rival and excludable is private; non-rival and non-excludable is public; non-rival and excludable is club; rival and non-excludable is common resource.
5If the question mentions people enjoying without paying, think free rider and under-provision.
6If the question asks who should supply it, a pure public good points to government provision through taxes.
7Check the options against the exact words in the question before marking.

Quickest way: Two-question grid

When to use it: Use for any one-line MCQ asking you to classify a good or pick the correct feature.

Draw a mental 2×2 grid: rows rival and non-rival, columns excludable and non-excludable.
Fix the corners: rival+excludable is private; non-rival+non-excludable is public.
Remember the mixed corners: club is excludable, common resource is rival.
Eliminate options that pair a feature with the wrong type, for example a public good described as excludable.
If a word like 'free rider' appears, choose the option about non-payment and market failure.
If you cannot decide between two goods, skip and return; a wrong answer costs 0.25.

Common mistakes in Public Goods vs Private Goods

Calling any government-provided good a public good.
Students link 'public' with 'government'. Governments also supply goods like education and healthcare that are partly rival and excludable.
Fix: Classify by rivalry and excludability, not by who supplies it.
Mixing up club goods and common resources.
Both are in-between types and the names sound similar.
Fix: Remember: club goods let you exclude (club has a gate); common resources are rival (fish run out).
Saying public goods are non-rival but excludable.
Students remember only one feature and guess the other.
Fix: A pure public good needs both features: non-rival and non-excludable.
Thinking the free rider problem means people cheat the law.
The word 'free' suggests theft.
Fix: It means someone enjoys a benefit without paying because they cannot be excluded. It is a market problem, not a crime.
Treating a road as always a public good.
Roads look like standard public goods.
Fix: An open uncongested road is close to public. A congested road becomes rival, and a toll road is excludable.

Worked examples

Example 1

Which of the following is a pure public good? (a) A packet of biscuits (b) National defence (c) A cable TV subscription (d) Fish in the open sea

Show the solution

Test (a): biscuits are consumed by one person and the seller can refuse sale, so rival and excludable: private.
Test (b): defence protects everyone, one more citizen does not reduce protection, and no one can be left out: non-rival and non-excludable.
Test (c): cable TV can be cut off for non-payers, so excludable: club good.
Test (d): ocean fish are rival because catches reduce stock, and access is open: common resource.

Answer: (b) National defence

Example 2

The free rider problem arises mainly because public goods are: (a) Rival in consumption (b) Non-excludable (c) Very expensive to produce (d) Supplied only by the government

Show the solution

Free riding means benefiting without paying.
This is possible only if non-payers cannot be stopped from using the good, which is non-excludability.
Option (a) is wrong because public goods are non-rival.
Option (c) is a claim about cost, which is not the cause of free riding.
Option (d) describes who supplies them, not why free riding occurs.

Answer: (b) Non-excludable

Example 3

A good is non-rival but people can be stopped from using it unless they pay. It is best described as: (a) Private good (b) Pure public good (c) Club good (d) Common resource

Show the solution

Non-rival rules out private good and common resource, which are both rival.
Excludable rules out pure public good, which is non-excludable.
Non-rival with excludable matches the club good.

Answer: (c) Club good

Exam tips

Most questions are one-line classifications. Learn the 2×2 grid and you can answer in seconds.
Watch the words 'pure' and 'mixed'. Pure public goods need both non-rivalry and non-excludability.
Link the free rider problem to market failure and government provision through taxes; options often test this link.
Examples are tested often: lighthouse, defence, street lights as public; food and clothes as private.
Do not guess between two close options; with 0.25 negative marking, skip and return if unsure.

Practice questions from Public Finance

Public Goods vs Private Goods: frequently asked questions

What is the difference between public goods and private goods?

A private good is rival and excludable, so one person's use reduces availability and non-payers can be kept out. A public good is non-rival and non-excludable, so use by one does not reduce others' use and no one can be excluded. Markets supply private goods well but tend to under-supply public goods.

What is the free rider problem with an example?

A free rider enjoys a good without paying. In a colony, if a private firm installs street lights, residents who refuse to pay still get light. If most residents reason this way, the firm earns nothing and stops supplying the lights.

What do non-rival and non-excludable mean?

Non-rival means one person's consumption does not reduce the amount available to others. Non-excludable means people who do not pay cannot be prevented from using the good. Both together define a pure public good.

Why does the government provide public goods?

Because of free riding, private firms cannot easily charge for them and may not produce them. The government funds them through taxes, which everyone must pay, so the cost is shared.