Heioo: New encyclopedia entry on Partial Equilibrium

2026-10-06T05:43:49Z

New encyclopedia entry on Partial Equilibrium

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'''Partial equilibrium''' analysis examines the determination of price and quantity in a single market, treating conditions in other markets as given. It is the standard method for analysing the effects of taxes, subsidies, price controls, and other interventions in a specific market, and it provides clear and tractable results at the cost of ignoring interactions among markets.

== Method and Assumptions ==
Partial equilibrium analysis assumes that the market under study is small relative to the economy, so that changes in it do not significantly affect prices or incomes elsewhere. Under this assumption, the demand and supply curves for the market can be analysed in isolation, and the effects of a change can be read off from the shift of the curves.

The method abstracts from general equilibrium effects, including changes in the prices of related goods, in factor prices, and in incomes. These effects can be important, particularly for large markets or for policies with wide reach, and their omission can lead to biased conclusions.

== Applications ==
Partial equilibrium analysis is used to evaluate the effects of taxes on a market. A tax shifts the supply curve upward, raising the price paid by consumers and lowering the price received by producers, with the difference equal to the tax. The incidence of the tax, the division of the burden between consumers and producers, depends on the elasticities of demand and supply.

The method is also used to analyse subsidies, price ceilings and floors, tariffs and quotas, and the effects of market power. In each case, the analysis identifies the change in price and quantity and the resulting changes in consumer and producer surplus, providing a measure of the welfare effects.

== Welfare Analysis ==
Partial equilibrium welfare analysis computes changes in consumer surplus, producer surplus, and government revenue. The change in total surplus measures the net welfare effect, which may be positive or negative depending on the policy and the presence of market failures.

Where market failures exist, such as externalities or market power, the intervention may improve welfare by correcting the failure. Where markets are competitive and complete, interventions generally reduce total surplus by distorting prices, and the analysis quantifies the loss.

== Relationship to General Equilibrium ==
General equilibrium analysis extends the analysis to all markets, accounting for interactions and feedback. The results of partial equilibrium analysis are often a good approximation when the market is small, but can be misleading when the market is large or when the policy has wide effects.

The choice between partial and general equilibrium analysis depends on the question and on the importance of interactions. Partial equilibrium is preferred for its clarity and tractability, while general equilibrium is used when the interactions among markets are central to the analysis.

== Tax Incidence ==
Tax incidence is a central application of partial equilibrium analysis. The division of the burden of a tax between buyers and sellers depends on the relative elasticities of demand and supply. The more inelastic side of the market bears the larger share of the burden, because it has less ability to change its behaviour in response to the tax.

This result has important implications for policy, since it determines who ultimately bears the cost of taxation. Taxes on goods with inelastic demand, such as necessities, tend to fall on consumers, while taxes on goods with elastic demand tend to fall on producers. The same logic applies to subsidies and to other interventions.

== Deadweight Loss ==
The welfare cost of a tax, the deadweight loss, arises from the reduction in the quantity traded relative to the efficient level. The loss is larger when demand and supply are more elastic, because the reduction in quantity is greater. It also increases with the square of the tax rate, so that high rates impose disproportionately large losses.

The analysis of deadweight loss informs the design of tax systems, favouring taxes on goods with inelastic demand or supply, which cause smaller reductions in quantity. It also informs the assessment of the optimal tax structure and the trade-off between revenue and efficiency.

== Price Controls ==
Partial equilibrium analysis is used to evaluate price ceilings and floors. A price ceiling below the market-clearing price creates excess demand, leading to shortages, queues, or rationing. A price floor above the market-clearing price creates excess supply, leading to surpluses and, in labour markets, to unemployment.

The analysis identifies the welfare effects of such controls, including the transfers between buyers and sellers and the deadweight loss from the reduction in quantity. It also clarifies the conditions under which controls may be justified, for example when market power or externalities cause prices to diverge from social costs.

== Trade Policy ==
Partial equilibrium analysis is used to evaluate tariffs and quotas. A tariff raises the domestic price, reducing imports and generating revenue, while imposing costs on consumers and, in the case of a large country, changing the terms of trade. The analysis identifies the distributional effects and the net welfare change.

For a small country that cannot affect world prices, a tariff reduces welfare by the deadweight loss from the reduction in imports and the distortion in consumption. For a large country, a tariff can improve the terms of trade, and the optimal tariff is positive, though retaliation and other considerations limit its use.

== Limitations ==
The limitations of partial equilibrium analysis arise from its abstraction from interactions among markets. Where a policy affects many markets or where the market under study is large, the general equilibrium effects may be significant, and the partial equilibrium conclusions may be misleading.

Examples include the effects of taxes on labour supply and on capital accumulation, which unfold over time and across markets, and the effects of trade liberalisation, which reallocates resources across sectors. In such cases, general equilibrium analysis provides a more complete picture, though at the cost of complexity.

== See also ==
* [[General Equilibrium]]
* [[Microeconomics]]
* [[Welfare economics]]

== References ==

<ref name="r1">Textbooks on microeconomic theory and welfare analysis.</ref>
<ref name="r2">Research on tax incidence and market interventions.</ref>
<ref name="r3">Analyses of the relationship between partial and general equilibrium.</ref>

<references />

[[Category:Microeconomics]]
[[Category:Welfare economics]]
[[Category:Econometrics]]

Partial Equilibrium - Revision history

Heioo: New encyclopedia entry on Partial Equilibrium