1.6 Classification of goods and services

A free good is available in enough quantity that no opportunity cost is normally required to use it. A private (economic) good is scarce, has an opportunity cost and can usually be made excludable through ownership or price.

The classification depends on context and technology. Air may be free in one setting but scarce and priced when cleaned or supplied in a cylinder.

A loaf of bread is a private good: using it leaves less for someone else and a seller can restrict access. Sunlight in an open field is usually treated as a free good.

“Free” means no opportunity cost, not merely zero money price; a free-to-user service may still use scarce resources.

A public good is non-rival: one person’s use does not substantially reduce another’s, and non-excludable: it is difficult to prevent non-payers from benefiting.

These properties create a free-rider problem, because individuals can wait for others to pay. Governments or collective arrangements may therefore provide the good, though congestion can make rivalry change at the margin.

A lighthouse signal can guide many ships at once and is difficult to withhold from a non-paying ship; national defence has similar properties.

Public does not mean government-produced and free does not mean no resource cost; the classification concerns rivalry and exclusion.

A merit good creates benefits that consumers may undervalue, so imperfect information can lead to under-consumption relative to the socially desirable level.

The market outcome reflects perceived private benefit, while education or vaccination may also create wider benefits. Policy can improve information, subsidise use or provide the good directly.

People may delay preventive health checks because they underestimate future benefits; reminders, information and subsidised access can increase uptake.

Calling a good merit does not mean every person must consume more; the economic issue is systematic information and welfare divergence.

A demerit good is consumed above the socially desirable level when consumers underestimate its harmful effects, often because information is imperfect or addictive behaviour distorts choice.

The market quantity reflects perceived private benefit and cost; education, regulation, taxation or age restrictions may reduce the gap, with trade-offs for liberty and enforcement.

A consumer may underestimate the long-run health cost of cigarettes, so an information campaign and excise tax can reduce consumption, though neither guarantees the socially optimal quantity.

A demerit good is not defined by being illegal or disliked; the key is systematic over-consumption relative to welfare.