What you'll learn
The labour market is a market like any other — demand, supply and a price that clears them — but with two features that make it distinctive. The price is a wage, which is somebody's income as well as somebody's cost, so the market carries an equity dimension the market for cement does not. And labour is supplied by people, who respond to more than money and cannot be produced to order.
Demand for labour is derived demand: firms want workers not for their own sake but for what they produce. So demand for labour depends on demand for the product, and the value a worker adds is measured by the marginal revenue product — the extra output they generate multiplied by the price it sells for. A profit-maximising firm hires up to the point where marginal revenue product equals the wage.
Supply depends on the wage available, the skills required, the training time, and the alternatives open to workers. Where skills take years to acquire, supply is inelastic and wages can stay high for long periods.
By the end you should be able to derive labour demand from marginal revenue product, explain what determines supply, account for wage differentials, and analyse minimum wages, monopsony and labour market imperfections.
Key terms and definitions
Derived demand — demand for a factor that arises from demand for the product it makes.
Marginal physical product (MPP) — the extra output produced by one more worker.
Marginal revenue product (MRP) — MPP multiplied by the price of the output; the value of the extra worker to the firm.
Wage differential — a persistent difference in wages between occupations, regions or groups.
Monopsony — a market with a single buyer. In labour, one dominant employer facing many workers.
Economic rent — payment to a factor above what is needed to keep it in its present use.
Transfer earnings — the minimum payment needed to keep a factor in its present use.
Minimum wage — a legal wage floor, effective only where set above the market wage.
Occupational immobility — inability to move between jobs because skills do not transfer.
Geographical immobility — inability to move between places, through housing cost, family ties or transport.
Core concepts
Demand for labour and marginal revenue product
A firm hires a worker if the worker adds more to revenue than to cost. The addition to revenue is the marginal revenue product: the extra output the worker produces, valued at the price it sells for.
So the firm hires up to the point where MRP equals the wage. Beyond that point an additional worker costs more than they bring in.
Because marginal physical product eventually falls — the law of diminishing returns — MRP eventually falls too, which gives the demand curve for labour its downward slope. A higher wage means fewer workers are worth employing.
Demand for labour therefore rises when demand for the product rises (raising its price and so MRP), when workers become more productive, or when the price of the output rises for any other reason. That is what derived demand means in practice: a collapse in tourism reduces demand for hotel workers without anything about those workers changing.
Supply of labour
The supply of labour to an occupation depends on the wage relative to alternatives, the qualifications and training time required, working conditions and status, and geographical location.
Supply is inelastic where training takes years, where qualifications are legally required, or where few people have the aptitude. It is elastic where the work requires little specific training and workers can move in easily from other occupations.
That elasticity is the main determinant of how long a wage advantage persists. A shortage of unskilled labour is quickly filled; a shortage of anaesthetists is not, because the training pipeline is years long.
Wage differentials
Why do wages differ so persistently between occupations? Several reasons combine, and a good answer gives more than one.
Differences in MRP: workers whose output is more valuable are worth more to employers. Differences in supply elasticity: occupations requiring long training have restricted supply. Compensating differentials: unpleasant, dangerous or antisocial work must pay more to attract workers, other things equal. Immobility: workers who cannot move between occupations or regions cannot compete away a differential. Trade union power and legal restrictions: entry to some professions is controlled. Discrimination: differentials not explained by productivity.
The analytical move that earns marks is to explain a specific differential by naming which of these apply, rather than listing all six.
Economic rent and transfer earnings
Any payment to a worker splits into transfer earnings — the minimum needed to keep them in this job rather than their next best alternative — and economic rent, the surplus above that.
Where supply is very inelastic, most of the payment is economic rent: a highly specialised worker with few alternative uses for their skill would stay for far less, so the excess is rent. Where supply is elastic, most of it is transfer earnings, since a small wage cut would send workers elsewhere.
The idea explains why a tax on a factor in very inelastic supply changes behaviour little — it takes rent rather than transfer earnings.
Minimum wages
A minimum wage set above the market wage raises pay for those who keep their jobs, and in the standard competitive model it reduces employment: at the higher wage fewer workers are worth employing, while more want to work, so there is excess supply of labour.
The evaluation is more interesting than that standard result suggests. Where the employer is a monopsonist — a single dominant buyer of labour — the firm already holds wages below the competitive level, so a minimum wage can raise both wages and employment up to the competitive point. That is a genuine theoretical result, not a debating trick, and it explains why the empirical evidence on minimum wages is mixed rather than uniformly negative.
Other considerations: higher wages may raise productivity and reduce turnover; they raise firms' costs, which may be passed to consumers; and where enforcement is weak the main effect may be to push employment into the informal sector — a live concern in Caribbean labour markets.
Monopsony and trade unions
A monopsonist facing an upward-sloping labour supply curve must raise the wage for all workers to attract one more, so the marginal cost of labour exceeds the wage. It therefore employs fewer workers at a lower wage than a competitive market would.
A trade union facing a monopsonist can bargain the wage up towards the competitive level without costing jobs, which is the strongest theoretical case for unions. Against a competitive employer, a union wage above the market level reduces employment in the standard model.
Unions also affect productivity in both directions: they may improve it through training, grievance procedures and lower turnover, or reduce it through restrictive practices. That two-sidedness is what an evaluation question is looking for.
Worked examples
Example 1 — Deriving labour demand from MRP (6 marks)
A firm sells its output at $20 per unit. Marginal physical product is 9, 8, 6, 5 and 3 units for the first through fifth worker.
MRP = MPP × $20: $180, $160, $120, $100, $60.
At a wage of $100, the firm hires up to the worker whose MRP equals the wage — four workers, since the fourth adds $100 and the fifth would add only $60 against a $100 cost.
At a wage of $160 the firm hires two workers. A higher wage means fewer workers are worth employing, which is the labour demand curve sloping downward.
Note that MRP falls because MPP falls, which is the law of diminishing returns showing up in the labour market.
Example 2 — A fall in product price (4 marks)
The output price falls from $20 to $10 because demand for the product has collapsed.
New MRP: $90, $80, $60, $50, $30.
At an unchanged wage of $100, no worker is now worth employing — even the first adds only $90.
Nothing about the workers changed. Demand for labour fell entirely because demand for the product fell, which is exactly what derived demand means, and it is why tourism-dependent labour markets are so exposed to external shocks.
Example 3 — Economic rent and transfer earnings (5 marks)
A specialist technician earns $90,000. The best alternative use of their skills would pay $35,000.
Transfer earnings = $35,000 — the minimum needed to keep them in this job. Economic rent = $90,000 − $35,000 = $55,000.
Because the skill is scarce and hard to substitute, supply is inelastic and most of the payment is rent. A tax on that rent would not drive the technician out of the occupation, since they would still earn well above their next best alternative — which is why taxes on factors in inelastic supply distort behaviour least.
Example 4 — Evaluating a minimum wage (6 marks)
A government sets a minimum wage above the market rate in a competitive labour market.
Standard prediction: at the higher wage fewer workers are worth employing while more wish to work, so employment falls and there is excess supply of labour — unemployment among exactly the low-paid workers the policy intended to help.
Qualifications: where employers hold monopsony power, wages are already below the competitive level, so the minimum wage can raise both pay and employment. Higher wages may also raise productivity and cut turnover, partly offsetting the cost. And where enforcement is weak, the effect may be displacement into informal employment rather than job loss.
Conclusion: the employment effect depends on the structure of the labour market and on the level at which the minimum is set. A modest minimum in a market with concentrated employers is defensible; a high one in a competitive market with weak enforcement is likely to cost jobs or push them into the informal sector. Naming those conditions is what the evaluation marks reward.
Common mistakes and how to avoid them
Forgetting that demand for labour is derived. It depends on demand for the product, not on anything about the workers themselves.
Confusing marginal physical product with marginal revenue product. MRP is MPP multiplied by the output price.
Saying a minimum wage always reduces employment. Under monopsony it can raise both wages and employment.
Setting a minimum wage below the market wage and expecting an effect. Like any floor, it binds only above the market level.
Explaining a wage differential with one reason. Several usually combine; name the ones that apply to the case.
Treating all of a high wage as economic rent. Transfer earnings are the part needed to keep the worker in the job.
Ignoring immobility. Differentials persist partly because workers cannot or will not move.
How this links to your Internal Assessment
The labour market gives an Internal Assessment a question with visible local relevance — wage differentials between sectors, the effect of a minimum wage, skill shortages, or migration of trained workers.
If you study a differential, collect wage data for two occupations and then explain the gap using the determinants above. Which occupation has restricted supply, and why? Is there a compensating differential for difficult conditions? Explaining a real gap with named mechanisms is far stronger than describing it.
Emigration of skilled workers is a particularly apt Caribbean topic. Frame it as labour supply responding to wage differentials across borders, and consider what raising domestic wages would cost against what losing trained workers costs. That framing turns a familiar complaint into economics.
Where you survey employers or workers, be careful about what the data supports. A small sample tells you about those respondents, and saying so while still drawing a tentative conclusion is better analysis than generalising from a handful of interviews.
Exam technique for the labour market and wages
MRP questions are calculation questions, so set the schedule out in columns: workers, MPP, output price, MRP. Then state the employment level at the given wage explicitly, since that is what the question asks for.
For minimum wage questions, give the standard competitive result first, then the monopsony qualification. Answering with only one of the two is the difference between a middling and a strong response.
Wage differential questions want several determinants applied to the specific case, not a list. Two or three developed properly beat six named.
Command words are consistent. Define derived demand wants the precise idea. Calculate MRP wants the multiplication shown. Explain why wages differ wants mechanisms applied to the occupations given. Discuss trade union power wants both the monopsony case and the competitive case. Evaluate a minimum wage wants the standard result, the qualifications, and a conclusion naming the conditions.
Where a question concerns a Caribbean labour market, the informal sector and skilled emigration are both genuinely relevant, and examiners reward their use.
Quick revision summary
- Demand for labour is derived from demand for the product.
- MRP = marginal physical product × output price; the firm hires where MRP equals the wage.
- MRP falls because MPP falls, which gives labour demand its downward slope.
- Supply of labour depends on the wage, training time, qualifications, conditions and location.
- Supply is inelastic where training is long — which is why some wage advantages persist for years.
- Wage differentials: MRP differences, supply elasticity, compensating differentials, immobility, union power, discrimination.
- Transfer earnings are the minimum needed to keep a worker in the job; economic rent is the surplus above it.
- Where supply is inelastic, most of the payment is rent, so a tax on it changes behaviour little.
- A minimum wage binds only above the market wage.
- In a competitive market it raises pay for those employed and reduces employment.
- Under monopsony it can raise both wages and employment, because the employer was holding wages below the competitive level.
- A monopsonist employs fewer workers at a lower wage; a union facing one can raise wages without costing jobs.
- Weak enforcement can displace employment into the informal sector rather than eliminating it.