A minimum wage causes unemployment in the standard competitive labour market model when it is set above the equilibrium wage. The higher legal wage increases the quantity of labour supplied while reducing the quantity of labour demanded, creating excess supply of labour, which the model represents as unemployment.
The qualification "in theory" is essential. The prediction depends on assumptions including competitive markets, enforceable wage legislation and downward-sloping labour demand. Real labour markets may contain monopsony power, search frictions, productivity effects and imperfect enforcement, so actual employment effects can be smaller, zero or occasionally positive.
What is a minimum wage?
A minimum wage is the minimum remuneration an employer is legally required to pay a worker for work performed during a given period. It is a form of price floor, with the wage rate treated as the price of labour.
Governments introduce minimum wages primarily to protect workers from unduly low pay and improve equity. They may also aim to reduce wage inequality, strengthen the bargaining position of low-paid workers and raise the incomes of employed households.
For the labour market model, distinguish between two possible positions of the wage floor:
| Position of minimum wage | Economic term | Predicted effect |
|---|---|---|
| Below or equal to the equilibrium wage | Non-binding minimum wage | No direct effect because the market wage already satisfies the law |
| Above the equilibrium wage | Binding minimum wage | Quantity of labour supplied exceeds quantity demanded |
A minimum wage does not automatically cause unemployment. The standard prediction applies only when the wage floor is binding, meaning it prevents the wage from settling at its market-clearing level.
Students can place this concept within the broader IB Economics role of government in microeconomics explained, with exam-focused resources. The current IB Economics course treats price controls as part of government intervention in microeconomics, building on demand, supply and competitive market equilibrium.
How the competitive labour market reaches equilibrium
In the simplified IB Economics labour market, households supply labour and firms demand it. The vertical axis shows the wage rate, while the horizontal axis shows the quantity of labour, which may be measured in workers or labour hours.
The demand for labour slopes downward. The supply of labour slopes upward. Their intersection determines the equilibrium wage, We, and equilibrium employment, Qe.
Why labour demand slopes downward
Labour demand is a derived demand because firms demand workers for the goods and services those workers help produce. Firms do not normally hire labour for its own sake. They hire when the revenue generated by an additional worker justifies the cost of employing that worker.
As the wage rate rises, firms may demand less labour for two main reasons:
- Substitution effect: Labour becomes more expensive relative to machinery, software or other productive inputs, encouraging firms to substitute away from labour.
- Scale effect: Higher labour costs increase production costs. If firms reduce output or if higher prices reduce sales, fewer workers are required.
The principle of diminishing marginal returns also helps explain the curve. Holding other inputs fixed, each additional worker may add less output than the previous one, so firms are willing to employ additional labour only at progressively lower wage rates.
Why labour supply slopes upward
At a higher wage, paid employment becomes more attractive relative to leisure, education, caring responsibilities or other uses of time. Existing workers may offer more hours, while people previously outside this particular labour market may begin seeking work.
Labour supply therefore tends to increase as the wage rises, ceteris paribus. This is a simplified market supply relationship, not a claim that every individual worker will always work more at every higher wage.
For a review of the underlying model, use RevisionDojo's competitive market equilibrium resources and supply and demand explanation.
Why does a minimum wage cause unemployment in theory?
Suppose the labour market initially clears at wage We and employment Qe. The government then introduces a minimum wage Wmin above We.
The theoretical sequence is:
- Employers are legally prevented from paying less than Wmin.
- The higher wage increases firms' cost of hiring labour.
- Firms move upward along the labour demand curve and reduce employment from Qe to Qd.
- The higher wage attracts more people or working hours into the market, increasing labour supplied from Qe to Qs.
- At Wmin, labour supplied exceeds labour demanded.
- The gap Qs minus Qd is excess supply of labour, represented as unemployment in the model.
The relationship can be written as:
Excess supply of labour = Qs - Qd
This is the central supply-and-demand argument behind minimum wage unemployment theory. Because wages cannot fall below the legal floor, the normal price mechanism cannot remove the surplus by lowering the wage back toward We.
What the diagram should show
A clear IB diagram should contain the following labels:
| Diagram element | Correct label or position |
|---|---|
| Vertical axis | Wage rate |
| Horizontal axis | Quantity of labour |
| Labour demand | Downward-sloping DL curve |
| Labour supply | Upward-sloping SL curve |
| Initial equilibrium | Intersection at We and Qe |
| Binding minimum wage | Horizontal Wmin line above We |
| Labour demanded at Wmin | Qd, read from the demand curve |
| Labour supplied at Wmin | Qs, read from the supply curve |
| Unemployment | Horizontal distance from Qd to Qs |
Do not draw the wage floor below equilibrium and then claim that it reduces employment. A floor below We is non-binding because employers were already paying a wage that complies with it.
RevisionDojo's price-control analysis and unintended consequences can help connect this labour-market case to the general price-floor model.
Job losses are not the same as total excess labour supply
A precise answer distinguishes the fall in employment from the total unemployment shown by the diagram. Employment falls from Qe to Qd, so the number of jobs lost relative to the original equilibrium is Qe - Qd.
However, the diagram's excess supply is Qs - Qd. This is larger because it includes both:
- workers displaced as employment falls from Qe to Qd; and
- additional people attracted into the labour market as labour supplied rises from Qe to Qs.
For example, suppose equilibrium employment is 1,000 workers. At a binding minimum wage, firms demand 900 workers while 1,100 people wish to work. Employment has fallen by 100, but excess supply equals 200 because another 100 people have entered the labour market seeking the higher wage.
In official labour statistics, a person generally must satisfy particular conditions, such as being available for and actively seeking work, to be classified as unemployed. The IB diagram abstracts from these measurement details and uses excess labour supply to represent the unemployment pressure created by the wage floor.
Which workers are most exposed to the theoretical effect?
A single national minimum wage does not bind equally in every occupation or region. It is more likely to affect markets in which the original equilibrium wage is relatively low.
The theoretical risk may therefore be greater for:
- young or inexperienced workers;
- workers with fewer recognised qualifications;
- employees in low-productivity occupations;
- workers in lower-wage regions;
- people attempting to enter formal employment for the first time.
The model does not say that these workers are less valuable as people. It predicts that if the legal hourly cost of employing a worker exceeds the revenue the firm expects that worker to generate, the firm may not offer the job.
Adjustment does not have to occur entirely through redundancies. Firms might reduce recruitment, leave vacancies unfilled, shorten operating hours, cut employees' hours, increase work intensity, automate tasks or raise prices. Consequently, a study looking only at immediate dismissals may miss other forms of labour-market adjustment.
Why the real-world effect may differ from the model
The competitive model gives a clear conditional prediction, not a universal empirical law. The International Labour Organization notes that measured employment effects vary across countries and studies, while reviews of international evidence often find that employment effects have been modest for the minimum wage changes studied.
| Reason the effect varies | Why it matters |
|---|---|
| Size of the increase | A small increase may remain close to equilibrium, while a very high floor is more likely to restrict hiring |
| Elasticity of labour demand | More elastic demand produces a larger reduction in employment for a given wage increase |
| Productivity changes | Better morale, training or lower staff turnover may offset part of the higher wage cost |
| Price increases | Firms may pass some costs to consumers instead of reducing employment |
| Profit margins | Some firms can absorb higher costs through lower profits |
| Economic growth | Rising demand for products can support labour demand despite higher wages |
| Coverage and enforcement | Weak enforcement may shift workers into informal employment rather than measured unemployment |
| Time period | Automation, relocation and changes to business models may take longer than immediate staffing adjustments |
The incidence of the policy also matters. Workers who keep their jobs receive a higher wage, but workers who lose employment or cannot obtain a first job may be worse off. This means an evaluation should consider the distribution of benefits and costs, not merely the average wage.
The monopsony exception
The most important theoretical qualification is monopsony power, meaning employers have some wage-setting power because workers have limited alternative employment options. Sources of this power include employer concentration, transport difficulties, incomplete information, recruitment costs and workers' reluctance or inability to move.
A monopsonistic employer may restrict employment and pay a wage below the competitive level. In that case, a carefully set minimum wage can raise both wages and employment by limiting the employer's power without yet making labour prohibitively expensive.
Recent research published in The Review of Economic Studies found more positive minimum-wage employment effects in more concentrated labour markets. This supports the idea that market structure affects the result. It does not mean that any minimum wage will increase employment, because a floor set sufficiently high can still reduce the quantity of labour demanded.
A strong IB evaluation therefore states:
- In a competitive labour market, a binding minimum wage is predicted to reduce employment and create excess labour supply.
- In a labour market with monopsony power, a moderate minimum wage may raise wages with little employment loss and may sometimes increase employment.
- At a sufficiently high wage floor, negative employment effects become more likely under either model.
How to explain the theory in an IB Economics exam
For an "explain" question, build a causal chain rather than writing that labour is simply "too expensive." An effective response should:
- Define the minimum wage as a legal wage floor.
- Establish the initial labour-market equilibrium at We and Qe.
- Place Wmin above We and identify it as binding.
- Explain why labour demand contracts to Qd.
- Explain why labour supply extends to Qs.
- Identify Qs - Qd as excess supply of labour or unemployment.
- Refer directly to the diagram throughout the explanation.
For an evaluative response, examine the wage floor's level, elasticities, affected workers, time period, enforcement and degree of employer power. Then reach a conditional judgment: the prediction is strongest when the minimum wage is far above equilibrium and labour demand is elastic in a competitive, well-enforced market.
Avoid claiming that empirical evidence "disproves" supply and demand. Evidence showing little employment loss may indicate that the increase was not strongly binding, demand was inelastic, firms adjusted through other channels or the labour market was not perfectly competitive. Economic models should be evaluated by examining their assumptions and relevance to the case.
To practise, use the IB Economics Questionbank, the targeted role of government in microeconomics questions and the corresponding price-control flashcards. Jojo AI can help identify missing labels or incomplete causal links, but redraw the diagram and reconstruct the explanation independently afterward.
Common mistakes to avoid
- Saying every minimum wage causes unemployment, without specifying that it must be binding in the standard model.
- Labelling firms as suppliers of labour. Firms demand labour, while households or workers supply it.
- Confusing Qe - Qd, the fall in employment, with Qs - Qd, total excess labour supply.
- Shifting the demand and supply curves when the wage floor initially causes movements along them.
- Drawing the minimum wage below equilibrium while describing it as effective.
- Treating the theoretical result as conclusive proof of what happens in every real economy.
- Claiming a higher wage only reduces demand, without explaining why more labour is also supplied.
Conclusion
In the standard IB Economics labour market model, a minimum wage causes unemployment when it is fixed above the equilibrium wage. Firms demand less labour, more workers supply labour, and the resulting gap Qs - Qd is excess supply of labour.
The result is conditional rather than automatic. Its size depends on how binding the wage is, labour demand elasticity, employer responses, enforcement and the competitiveness of the labour market. RevisionDojo's study notes, flashcards and Questionbank can help you practise the diagram, while Jojo AI is useful for checking whether your written explanation links each stage of the model logically.
Sources and referenced URLs
- International Baccalaureate: Diploma Programme Economics
- International Labour Organization: Definition and purpose of minimum wages
- International Labour Organization: Minimum Wage Policy Guide
- Review of Economic Studies: Minimum Wage Employment Effects and Labour Market Concentration
- UK government review of international minimum-wage evidence
- RevisionDojo: Role of Government in Microeconomics notes
- RevisionDojo: Demand and supply forming market equilibrium
- RevisionDojo: Supply and demand explained
- RevisionDojo: Unintended effects of price controls
- RevisionDojo: IB Economics Questionbank
- RevisionDojo: Role of Government in Microeconomics Questionbank
- RevisionDojo: Role of Government in Microeconomics flashcards
