Determination of Wage Differentials (Cambridge (CIE) A Level Economics): Revision Note

Determination of wage differentials by labour market forces

• Wage differentials are differences in pay between workers across occupations, industries and firms

  • In competitive labour markets, these are determined primarily by the interaction of labour demand and labour supply

• The equilibrium wage in any labour market is set where demand for labour equals supply of labour

  • Workers in markets with high demand and restricted supply earn more than those in markets with low demand and abundant supply

• The starting point for explaining any wage differential is marginal revenue product (MRP) theory: a firm's demand for labour is derived from the value that an additional worker adds to output

  • A worker's MRP = marginal product × price of the good or service produced

  • Firms hire up to the point where MRP = wage rate

    • workers whose MRP is higher will command higher wages

1. Differences in the demand for labour

• Higher demand for labour raises the equilibrium wage, shifting the demand curve for labour to the right and increasing the wage rate at any given level of supply

• Demand for labour is a derived demand — it depends on the demand for the final good or service the worker helps produce

  • A Premier League footballer generates enormous revenues for their club — their MRP is very high, so clubs are willing to pay exceptionally high wages

  • A supermarket cashier contributes to the sale of low-margin goods — their MRP is modest, and wage rates reflect this

• Changes in the demand for skills can widen or narrow differentials over time

  • Rising demand for data scientists and software engineers — driven by rapid growth in the technology sector — has shifted their labour demand curve significantly to the right, raising wages substantially relative to other graduate occupations

2. Differences in the supply of labour

• Restricted supply of labour pushes wages up

  • Where few workers can do a job, employers must offer higher wages to attract and retain staff

• Supply of labour to an occupation depends on:

  • Length and cost of training

    • Becoming a surgeon requires over a decade of training; the supply of surgeons is highly inelastic, sustaining high wages even when demand is relatively stable

  • Non-monetary characteristics of the job

    • Dangerous, unpleasant, or antisocial-hours work requires a compensating wage differential to attract workers

  • Barriers to entry

    • Professional licensing, qualifications, and union membership restrictions all limit the supply of labour, keeping wages above the level that would prevail in a fully competitive market

The role of elasticity of supply

• Where supply is wage-inelastic, even a small rightward shift in demand produces a large increase in the wage rate

  • This explains extreme differentials at the top of the earnings distribution

3. Compensating wage differentials

• Some wage differentials arise not from skill differences but from the characteristics of the job itself

• Workers must be compensated for jobs that are:

  • physically dangerous (e.g. deep-sea fishing, construction)

  • unpleasant or socially stigmatised

  • requiring unsociable hours or significant geographical mobility

• These compensating differentials are a labour market force

  • Without them, supply to these occupations would fall, creating labour shortages