Labour Market: Minimum wage, monopsony — Edexcel A-level Economics

SPEC 3.5 • LABOUR MARKET

Minimum Wage & Monopsony

The monopsony model, MFC & exploitation, minimum wage in competitive vs monopsony markets, Card & Krueger, trade unions, bilateral monopoly, and the counter-intuitive result that wins Level 4

Key Definitions

Monopsony

A market where there is a single buyer — in the labour market, a single employer that dominates hiring in a local or occupational market.

Marginal Factor Cost (MFC)

The additional cost of hiring one more worker. For a monopsonist, MFC > Wage because raising the wage for one extra worker means raising it for ALL existing workers too.

Bilateral Monopoly

When a trade union (monopoly seller of labour) faces a monopsonist employer (monopoly buyer of labour). The wage outcome is indeterminate — depends on relative bargaining power.

Why MFC Exceeds the Wage

A monopsonist faces an upward-sloping supply of labour curve. To attract one more worker, it must raise the wage — but this higher wage applies to all workers, not just the new hire.

Worked Example

WorkersWage (£)Total Wage Bill (£)MFC (£)102002,000—112102,310310122202,640330The 11th worker is paid £210, but hiring them costs £310 because the wage rise (£10) also applies to the original 10 workers (10 × £10 = £100 extra). So MFC = £210 + £100 = £310.

MFC = Wage + (ΔWage × existing workers)

This is why the MFC curve lies above and is steeper than the SL curve on the monopsony diagram.

Monopsony Labour Market Diagram

(See the fully labelled diagram on the summary sheet — the key relationships are shown below)

Reading the Monopsony Diagram — 5 Steps

Draw: DL = MRP (downward), SL = ACL (upward), MFC (above SL, steeper)

Monopsony sets: MFC = MRP → determines employment Lm

Read wage: from SL at Lm → Wm (BELOW competitive wage)

Exploitation gap: vertical distance from Wm up to MRP at Lm — workers paid less than their MRP

Compare: Competitive outcome would be W*, L* (where DL = SL) — monopsony gives LOWER wages AND LOWER employment

Minimum Wage — Competitive Market

In a competitive labour market, a minimum wage set above equilibrium creates a standard wage floor result.

Wmin > W*

Excess supply of labour

L₁ employed, L₂ want to work

Unemployment = L₂ − L₁

The Counter-Intuitive Result ⭐

In a monopsony labour market, a minimum wage set between Wm and W* can INCREASE both wages AND employment simultaneously.

Why It Works

Before: Monopsonist sets MFC = MRP → hires Lm workers at Wm (below competitive level)

Minimum wage imposed: Wmin set between Wm and W*

MFC flattens: Up to the point where Wmin meets the original SL, the firm faces a flat MFC = Wmin (no longer needs to raise wages to attract more workers)

Result: With a lower effective MFC, it becomes profitable to hire more workers

Outcome: Wages ↑ (Wm → Wmin) AND employment ↑ (Lm → Lmin)

Card & Krueger (1994)

Empirical evidence from fast food restaurants in New Jersey found that a minimum wage increase did NOT reduce employment — consistent with monopsony power in low-wage labour markets. This is the classic Level 4 evidence reference.

Minimum Wage — Two Models

Competitive Market

Wmin above W* → unemployment

Excess supply = L₂ − L₁

Higher wage but fewer jobs

Firms face higher ATC → cost-push pressure

Standard textbook result

Monopsony Market

Wmin between Wm and W* → ↑ wages AND ↑ employment

Corrects exploitation gap

MFC flattens → profitable to hire more

Card & Krueger evidence supports

Level 4 analysis point

Examiner Alert

Students who only analyse the competitive model for a minimum wage question score maximum Level 3. To reach Level 4, you MUST reference the monopsony model and explain that the employment effect depends on the degree of employer market power.

Trade Unions

Trade Union

An organisation of workers that negotiates collectively with employers over wages, conditions, and employment levels.

In a competitive market, a trade union acts as a monopoly supplier of labour — it restricts supply to raise wages above competitive equilibrium. This mimics the minimum wage diagram: wages rise, but employment may fall.

Union Wage Premium

Unionised workers in the UK earn approximately 10–15% more than non-unionised workers in similar roles. This is strong empirical evidence for the essay.

Bilateral Monopoly

When a trade union (monopoly seller) faces a monopsonist employer (monopoly buyer), the wage outcome is indeterminate. It depends on relative bargaining power. Generally leads to a wage closer to the competitive level than either side alone would achieve.

Example: NHS nurses' union vs NHS trust. One powerful employer, one powerful union. The resulting wage reflects the balance of power between the two.

Macroeconomic Effects of Minimum Wage

Minimum wage questions often require both micro and macro analysis. The macro chain unlocks cross-synoptic marks.

Positive Macro Effects

Higher wages→↑ disposable income→↑ consumption (C)→AD shifts right→Multiplier effect

Negative Macro Effects

Higher ATC for firms→SRAS shifts left→Cost-push inflation→Real wage gain eroded

The net effect on output depends on the relative magnitudes of the AD shift (positive) vs the SRAS shift (negative). This ambiguity is the evaluation.

AO4 Evaluation Toolkit

Evaluative ArgumentDevelopment

Elasticity of DLIf DL inelastic (healthcare, specialists) → small employment loss, wage gain dominates. If elastic (low-skill manufacturing) → significant job losses. Context-specific.

Monopsony powerWhere employers have monopsony power, minimum wage can raise BOTH wages and employment. Undermines simple competitive model. Card & Krueger evidence.

Time periodShort run: DL inelastic (can't automate quickly) → small effect. Long run: firms invest in automation → DL more elastic → larger employment loss.

Level of minimum wageSlight increase above W* → limited negative effects. Large increase → more significant unemployment. Depends how far above equilibrium.

Non-wage adjustmentsFirms may cut hours, reduce non-wage benefits (pensions), tighten zero-hours contracts. Headline employment figure doesn't capture full effect.

Inflation riskHigher wages → higher costs → firms pass on as higher prices → cost-push inflation → real wage gain may be less than nominal.

Common Errors — Examiner Reports

Monopsony Diagram Errors

MFC drawn below or parallel to SL — MFC must be ABOVE and STEEPER than SL

Reading wage from MFC instead of SL — the monopsonist pays the wage on the SL curve at Lm, NOT the MFC

Forgetting the exploitation gap — must show the vertical distance between MRP and Wm at Lm

Not showing the competitive comparison — always show W* and L* (where DL=SL) to contrast with Wm and Lm

Minimum Wage Errors

Only using the competitive model — maximum Level 3 without monopsony analysis

Stating minimum wage always causes unemployment — only in competitive markets; monopsony result is opposite

Not stating the model answer phrase: "In a competitive market the minimum wage causes unemployment. However, where monopsony power exists, a minimum wage set between Wm and W* can raise both wages and employment simultaneously — the net employment effect is ambiguous."

Practice Question

Question (25 marks): Evaluate the likely microeconomic and macroeconomic effects of a significant rise in the national minimum wage.

1

Define: Minimum wage = wage floor set above equilibrium. Thesis: effects depend on labour market conditions, degree of monopsony, and elasticity of DL.

2

KAA 1 — Micro (competitive): Wmin > W* → excess supply → unemployment = L₂ − L₁. Firms face higher ATC → may pass on as higher prices. DIAGRAM: labour market with wage floor.

3

KAA 2 — Micro (monopsony): Where employer has monopsony power, minimum wage between Wm and W* → increases BOTH wages and employment. MFC flattens. Card & Krueger evidence. DIAGRAM: monopsony with minimum wage correction.

4

KAA 3 — Macro: Higher wages → ↑ C → AD right → multiplier effect. BUT higher ATC → SRAS left → cost-push inflation. Net effect ambiguous.

5

Evaluation: (i) Elasticity of DL — sector-specific. (ii) Time period — SR inelastic, LR firms automate. (iii) Non-wage adjustments — hours cut, benefits reduced. (iv) Level of the rise — marginal vs significant increase.

6

Conclusion: "The net effect depends critically on the degree of monopsony power in the relevant labour markets and the elasticity of demand for labour. In sectors with significant employer power (retail, care work), a moderate rise is likely to improve wages with limited employment effects. In highly competitive sectors with elastic DL, employment losses may be more significant."

Summary

Key Facts

ConceptDetail

MonopsonySingle buyer. MFC > Wage. Pays Wm < W* and hires Lm < L*.

Exploitation gapMRP − Wm at Lm. Workers paid below their marginal revenue product.

Min wage (competitive)Wmin > W* → unemployment = L₂ − L₁

Min wage (monopsony)Wmin between Wm and W* → ↑ wages AND ↑ employment

Card & KruegerNJ fast food — min wage rise didn't reduce employment

Trade unionMonopoly seller of labour. ~10–15% wage premium.

Bilateral monopolyUnion vs monopsonist. Outcome indeterminate — depends on bargaining power.

The Golden Rule

Every minimum wage answer needs TWO models: competitive (unemployment) AND monopsony (corrective). The phrase "the net employment effect is ambiguous" is your ticket to Level 4. Then evaluate using elasticity, time period, and sector-specific context.