What causes income inequality to change in a country

Income inequality refers to the unequal distribution of earned and unearned income across individuals or households within an economy, typically measured using the Gini coefficient, where a value closer to one represents greater inequality. One primary cause of income inequality is the disparity in wages across different occupations and skill levels. In a market economy, wages are determined by the interaction of labour supply and demand; workers with specialised skills or qualifications face lower labour supply relative to demand, which pushes their wage rates higher. This means that a software engineer commands a significantly higher salary than an unskilled retail worker, widening the gap between those at the top and bottom of the income distribution. As a result, the increasing demand for high-skilled labour driven by technological change — often called skill-biased technological change — has contributed to a long-run rise in wage inequality in economies such as the UK. Furthermore, the ownership of productive assets such as property, shares, and financial capital generates investment income in the form of dividends, rent, and interest. Since asset ownership is itself highly concentrated among wealthier households, this compounds earned income inequality further. Government policy also plays a significant role: progressive taxation and transfer payments such as Universal Credit redistribute income from higher to lower earners, compressing inequality, whereas cuts to welfare spending or reductions in the top rate of income tax can widen it. Therefore, income inequality at any point in time reflects the combined effect of structural labour market forces, the distribution of capital ownership, and the extent of fiscal redistribution undertaken by the state.

• →Wage differentials and marginal revenue product: Pay differs across workers because firms pay according to a worker's contribution to revenue. High-skilled or highly productive workers generate more output per hour, so firms bid up their wages, while low-productivity workers in oversupplied labour markets receive much lower pay.
• →Skill-biased technological change: Automation and digitalisation substitute for routine, low-skill tasks while complementing high-skill cognitive work. This shifts labour demand away from low-wage workers and towards high-wage workers, structurally increasing the wage gap over time.
• →Unearned income and wealth concentration: Income inequality is amplified when a large share of national income flows as returns to capital — rent, dividends, and interest — because ownership of capital is far more concentrated than earned income. Piketty's observation that the rate of return on capital tends to exceed the rate of economic growth (r > g) explains why this reinforces itself over generations.
• →Monopsony power in labour markets: Where employers have monopsony power — for example, in local labour markets dominated by a single large employer — they can suppress wages below the competitive level, reducing the income of affected workers and widening inequality relative to workers in competitive markets.
• →Fiscal redistribution: Progressive income taxes, means-tested benefits, and public services such as education act as automatic stabilisers that compress the income distribution. Changes in the generosity or structure of the tax-benefit system are therefore a direct policy-driven cause of changes in measured inequality.

This question tests understanding of the determinants of the personal distribution of income — that is, how and why income is shared unequally across individuals and households in an economy. It draws on Edexcel spec point 4.2.2.c, which covers inequality and its causes, and AQA spec point 4.1.7.1 — The distribution of income and wealth, which requires students to analyse the factors that shape income and wealth distributions. Strong answers move beyond simply listing causes and instead explain the economic mechanisms — labour market theory, returns to capital, and fiscal policy — that determine how much income different groups receive.

Examined 5 times across AQA and Edexcel since 2017.

The topic has appeared on both boards and at a wide range of tariffs, reaching 25 marks in the October 2020 sitting.

• →Poverty and Inequality — directly relevant because understanding what drives income inequality is inseparable from understanding how poverty is defined and measured relative to the income distribution.