Concept Architecture
Concept
Theoretically, Equilibrium is the state of a system in which opposing economic forces are balanced and no participant has an incentive to alter their behaviour given prevailing conditions. In health economics, equilibrium most commonly refers to market equilibrium, where the quantity of healthcare demanded equals the quantity supplied, although equilibrium concepts also arise in insurance markets, game theory and general equilibrium analysis. The concept exists to characterise stable outcomes resulting from interactions between consumers, providers, payers and policymakers.
Mathematically, Equilibrium is represented by solving a system of equations or optimisation conditions in which relevant variables satisfy balance conditions simultaneously. In competitive markets, equilibrium is obtained where demand equals supply, while more complex health economic models may solve multiple simultaneous equations representing interacting markets, behavioural responses or strategic decisions. The mathematical framework identifies prices, quantities or strategies that satisfy equilibrium conditions.
In practice, Equilibrium is estimated by specifying demand and supply relationships, calibrating model parameters using observed data and solving for equilibrium values using analytical or numerical methods. Health economists use equilibrium analysis to evaluate policy interventions, reimbursement mechanisms, taxes, subsidies, insurance reforms and market regulations by comparing baseline and post-intervention equilibrium outcomes.
Purpose
Used to determine stable market, behavioural or strategic outcomes resulting from the interaction of economic agents and to estimate the effects of health policy interventions on prices, utilisation, welfare and resource allocation.
Mathematical Formulae
Primary Formula
For competitive market equilibrium:
Q?(P) = Q?(P)**
where:
- Q? = quantity demanded
- Q? = quantity supplied
- P* = equilibrium price
Supporting Formulae
Linear demand:
Q? = a ? bP
Linear supply:
Q? = c + dP
Equilibrium solution:
P = (a ? c)/(b + d)*
Q = a ? bP**
Related Mathematical Methods
- Simultaneous equation modelling
- Comparative statics
- Optimisation
- General equilibrium modelling
- Partial equilibrium analysis
- Fixed-point algorithms
- Numerical equation solving
Example
Suppose annual demand for a diagnostic test is:
Q? = 10,000 ? 100P
and annual supply is:
Q? = 2,000 + 60P
Equilibrium occurs when:
10,000 ? 100P = 2,000 + 60P
P = 50*
The equilibrium quantity is:
Q = 10,000 ? 100(50) = 5,000*
The model predicts an equilibrium price of �50 per test and annual utilisation of 5,000 tests. A reimbursement policy lowering provider costs would shift the supply curve and produce a new equilibrium.
Excel Implementation
| Function | Example Formula | Health Economics Application |
|---|---|---|
| Solver | Solve Demand - Supply = 0 | Determine equilibrium price and quantity. |
| GOAL SEEK | Set Demand=Supply by changing price | Find market-clearing price. |
| SUM | =SUM(B2:B20) | Aggregate market demand or supply across providers. |
| IF | =IF(Demand=Supply,""Equilibrium"",""Not at equilibrium"") | Check whether equilibrium conditions are satisfied. |
VBA (Optional)
Automate equilibrium calculations across multiple policy scenarios by repeatedly solving market-clearing conditions and recording resulting prices, quantities and welfare measures.
Sources
- Drummond MF, Sculpher MJ, Claxton K, Stoddart GL, Torrance GW. Methods for the Economic Evaluation of Health Care Programmes. 4th ed.
- Briggs A, Claxton K, Sculpher M. Decision Modelling for Health Economic Evaluation.
- Varian HR. Intermediate Microeconomics: A Modern Approach.
- Mas-Colell A, Whinston MD, Green JR. Microeconomic Theory.
- Arrow KJ. Uncertainty and the Welfare Economics of Medical Care. American Economic Review. 1963.
Related Concepts (2)
Library
Publications
1
Decision Modelling for Health Economic Evaluation — Briggs, Claxton & Sculpher, 1st Edition ed., 2006 (Oxford University Press)
Foundational textbook on decision-analytic modelling for economic evaluation, covering decision trees, Markov models, handling parameter and structural uncertainty, probabilistic sensitivity analysis, and value of information. Volume 1 in the Handbooks in Health Economic Evaluation series.
BookView source →
Frequently Asked Questions (6)
What is equilibrium in economics?
A state in an economic system where opposing forces, such as supply and demand, balance so there is no inherent tendency to change.
Source: Varian 2014
What kinds of equilibrium appear in economics?
Equilibrium is a general idea applied at several levels. A single market is in equilibrium when its price balances supply and demand, a whole economy is in general equilibrium when every market clears at once, and a strategic setting is in equilibrium, in the game-theoretic sense, when no player can gain by changing course alone. Each uses the same core notion of a state with no internal pressure to change, applied to a different system. Mas-Colell and colleagues (1995) set out these forms.
Source: Mas-Colell et al. 1995
How is equilibrium reached in a market?
In a market, equilibrium is reached through the adjustment of price to imbalances between supply and demand. If price is above the equilibrium, a surplus develops and pushes it down; if below, a shortage pushes it up. These pressures move the price toward the level where quantity supplied equals quantity demanded, at which point there is no further tendency to change. The adjustment process drives the market to equilibrium, where the plans of buyers and sellers are consistent.
Source: Varian 2014
Why is equilibrium a stable state?
Equilibrium is a stable state when, if the system is disturbed, forces act to return it toward equilibrium. In a market, a price above equilibrium creates a surplus that pushes price back down, and one below creates a shortage that pushes it up, so deviations are self-correcting. This is why the system tends to rest at equilibrium and to return there after a disturbance. Not all equilibria are stable, but stability is what makes equilibrium a useful description of where a system settles.
Source: Varian 2014
Is an economic equilibrium always efficient?
An economic equilibrium is efficient under the conditions of perfect competition, as the first welfare theorem shows, but not otherwise. Where there are externalities, public goods, market power, or information asymmetries, the equilibrium can be inefficient, settling at a point where welfare is not maximised. Equilibrium describes where a system comes to rest, given the forces acting on it, which is not necessarily the outcome that would maximise welfare, so equilibrium and efficiency are distinct.
Source: Varian 2014
Why is equilibrium a useful concept?
Equilibrium is useful because it predicts where an economic system will settle and how it will respond to changes: by finding the balance of opposing forces, it identifies the price and quantity a market will reach and how these shift when demand or supply changes. It provides a benchmark for analysing the effects of taxes, subsidies, and other interventions. Even where systems do not perfectly reach equilibrium, the concept clarifies the direction of adjustment and the tendencies at work.
Source: Varian 2014
Trust Record
Verified by Dr Darrin Baines
British health economist
Professional identity: darrinbaines.org
Verification date: 30 Sep 2025
Content version: 1.0.0
Canonical Identity
- Persistent URI
- https://healtheconomics.wiki/concept/equilibrium
- Term code
- HE-EM-DM-030
Stable URI · Machine-readable · Resolvable · CC BY 4.0