The labour market: demand, supply and wages

The big picture

Every business generates a surplus, and that surplus is divided between returns to labour (wages, salaries, benefits) and returns to capital (profit, dividends, interest, fees). Every Theme 3 essay is at bottom about what determines that division and who has the power to shift it: bargaining power, market structure, mobility, union density, legislation, immigration. Call it the surplus question, and keep it in view on every page of this section.

The evidence says the division has been moving against labour. The UK labour share of GDP fell from around 60% in the 1970s to about 54% by 2020 (ONS). Between 2000 and 2023 UK productivity rose roughly 25% while real median wages rose roughly 5%: the twenty point gap measures the share of productivity gains captured by capital rather than passed on in pay. The OECD found the labour share fell in 26 of 30 member countries between 1990 and 2015, so the shift is structural rather than a British quirk. This page builds the competitive machinery, where wages track productivity by construction; the pages that follow ask why, in practice, they so often do not.

The theory

A profit-maximising firm hires workers up to the point where the MRP of the last worker equals the marginal cost of employing them, which in a competitive labour market is the wage. Diminishing marginal productivity makes MRP fall as employment rises, so the labour demand curve slopes downward. Anything that raises MRP shifts the whole curve right: higher productivity, a higher product price or new revenue streams (a bigger broadcast deal, greater billing capacity), and investment in human capital through qualifications, specialist training and experience.

How far employment responds to a wage change depends on the elasticity of demand for labour. Where capital can substitute for workers, demand is elastic: platforms can automate or exit a market, and rising wage floors strengthen the business case for warehouse robotics and self-checkout, though always as a long-run margin rather than an overnight switch. Where the work is inherently local and resists automation, as with construction and retrofit, demand is inelastic and higher wages mostly get paid rather than avoided.

Supply is the mirror question: what induces workers to offer their labour to this occupation? Money matters (wages, bonuses, pensions), and so do non-monetary factors: flexibility, autonomy, job security, term-time working in teaching, set against unsociable hours and physical demands in warehouse work, portering and care. Each worker has a reservation wage, the effective wage needed to induce them to supply labour at all. The elasticity of labour supply depends on how quickly new workers can enter: a four to five year construction apprenticeship, a three year nursing degree or seven to fifteen years of medical training make supply inelastic, while a large surplus of qualified candidates (around 25,000 PhDs a year chasing roughly 3,000 permanent academic posts) makes supply highly elastic. In a competitive market the wage settles where demand meets supply, every firm takes that wage as given, and a differential between occupations attracts workers across until supply expands and the gap narrows. That last clause carries the whole theory: when a gap refuses to narrow, something is blocking the flow of workers, which is the subject of the next page.

Application

Football is the cleanest revenue chain in the course. Premier League domestic broadcast rights are worth around £2.5bn against roughly £0.7bn for the whole Championship, about 3.5 times more per club, and the median wage gap between the divisions is roughly tenfold: the demand for elite players is a function of the revenue their performances generate for the club rather than their ability in isolation. In an answer, quantify the revenue driver first, then shift the MRP curve, then land on the wage. The same discipline works in healthcare: consultants on £93k to £126k after thirteen to fifteen years of post-secondary training, against Band 5 nurses on £28,407 to £34,581, pairs a high MRP with a long pipeline that keeps supply inelastic. A trader generating £50m of directly attributable profit is the limiting case where MRP is almost perfectly measurable.

Supply-side facts earn their keep when you attach them to elasticity. Electricians, plumbers and gas engineers saw real wage rises of 25 to 35% between 2021 and 2024 because the four to five year training pipeline stopped supply responding; electrical installation apprenticeship starts did rise 15% in 2022–23, and those recruits arrive years later, so the premium persists in the meantime. At the other pole, the 8:1 ratio of new PhDs to permanent academic posts keeps university teaching supply elastic and hourly pay low, with 68% of teaching on insecure contracts (UCU, 2022). Use each figure as evidence for one specific link: the revenue driver sizes MRP, the pipeline sizes the supply elasticity, and the two together predict the wage.

Building the paragraph

A wage-differential essay almost always opens with an MRP paragraph. Give the topic sentence the mechanism, the direction and the headline evidence in one breath:

Because the demand for footballers is derived from the revenue they generate, the Premier League's £2.5bn domestic broadcast deal pushes its players' MRP, and therefore their wages, far above the Championship's.

1. Demand for players is derived demand: a club hires talent for the broadcast, gate and commercial revenue its performances generate, so the value of a player is the revenue he adds.
2. Premier League domestic broadcast rights of around £2.5bn dwarf the Championship's roughly £0.7bn, about 3.5 times more per club, so each unit of performance earns a multiple of the revenue one division down.
3. Since MRP is marginal product multiplied by the marginal revenue on that output, the same goal or clean sheet carries a far higher MRP in the Premier League.
4. Diagram step: draw the competitive labour market with the Premier League's MRP curve shifted right of the Championship's, and read off the higher equilibrium wage W₂ where the new demand meets supply.
5. The equilibrium wage and employment of top-flight players rise, and the observed differential matches the prediction: a median Premier League wage near £3.5m against a roughly tenfold gap to the Championship.
6. Supply cannot close the gap, because elite ability and academy training are scarce, so the differential persists rather than being competed away, exactly as the model predicts for inelastic supply.

Key terms

Term	Precise definition	Where it earns marks
Derived demand	Demand for labour arising from demand for the goods and services labour produces.	The AO1 opener of any labour demand paragraph; link it to a named revenue source.
Marginal revenue product	Marginal physical product multiplied by marginal revenue: the revenue added by one more worker.	Relabelling the demand curve MRP = D turns a generic diagram into labour market analysis.
Elasticity of demand for labour	The responsiveness of employment to a change in the wage, shaped by how easily capital substitutes for labour.	The hinge of every minimum wage and regulation evaluation: elastic demand means job losses.
Reservation wage	The effective wage needed to induce a worker to supply labour, raised by insecurity or caring obligations.	Explains supply decisions that headline wages alone cannot (AO3).
Elasticity of labour supply	The responsiveness of labour supplied to a wage change, governed by training pipelines and barriers to entry.	Predicts whether a demand shift raises mainly wages (inelastic) or mainly employment (elastic).
Competitive labour market	A market in which many firms hire identical labour and each takes the market wage as given.	The benchmark you state before showing where a real market departs from it.