For Cambridge OCR A Level Sociology, Castles and Kosack offer a Marxist explanation of ethnic inequality. Their work is especially useful because it links ethnicity to class inequality, capitalism and the organisation of the labour market.

Their best-known work, Immigrant Workers and Class Structure in Western Europe, examined the position of migrant workers in post-war Western Europe. Castles and Kosack argued that migrant workers were often pushed towards the lower levels of the labour market: low-paid, insecure, semi-skilled or unskilled work with poorer conditions. They saw this not as accidental, but as part of the way capitalism operates.

Capitalism and the reserve army of labour

A central idea in their work is the reserve army of labour. This is a Marxist concept describing a group of workers who can be drawn into employment when employers need labour, but who are also more vulnerable to unemployment or insecure work when demand falls.

Castles and Kosack argued that migrant workers could form part of this flexible workforce. Employers benefit from having workers available for difficult, low-status or poorly paid jobs, particularly in sectors where labour is needed quickly. In periods of economic growth, workers may be recruited into these jobs. In downturns, they may be more exposed to redundancy, casualisation or unemployment.

Their argument was that this flexibility benefits employers because it can reduce labour costs and weaken workers’ bargaining power. If workers fear being replaced, they may be less able to demand higher wages, better conditions or more secure contracts.

Contemporary UK evidence gives some support to this argument. Resolution Foundation research published in 2025 found that foreign-born workers were more likely to experience precarious work than UK-born workers. Among foreign-born workers without UK citizenship, around one in six were in precarious employment, compared with 11% of UK-born workers. Recent migrants were also more likely to be on variable-hours, temporary or zero-hours contracts.

The same research found that recent foreign-born workers were 2.4 times as likely as UK-born workers to be on flexible contracts even after differences in age, sex and qualifications were considered. It also identified sectors such as hospitality, administration and agriculture as areas where foreign-born workers and precarious work were both more common.

This does not prove that employers deliberately create ethnic inequality. However, it does suggest that some migrant workers remain more likely to experience the type of insecurity that Castles and Kosack associated with a reserve army of labour.

Ethnic inequality and insecure work

Castles and Kosack argued that migrant workers were often concentrated in the least desirable jobs. Current UK evidence shows that insecurity is still unevenly distributed across ethnic groups.

Research brought together by the Joseph Rowntree Foundation found that, in 2022–23, 7.3% of Black/African/Caribbean workers and 6.5% of Pakistani workers were on zero-hours contracts, compared with 3.1% of White workers. It also found that 12% of Black workers and 10% of Pakistani and Bangladeshi workers were in temporary employment, compared with 5% of White workers.

These figures fit with the Marxist view that ethnic inequalities are connected to labour-market position rather than simply individual choices. Workers who are concentrated in temporary, casual or low-security jobs may face less predictable income, fewer employment rights and greater difficulty planning their lives.

However, students should avoid claiming that all ethnic minority workers experience the same labour-market position. There are major differences between ethnic groups, between migrants and UK-born people, and between occupational sectors. Some ethnic minority groups are strongly represented in professional employment, while others face much greater exclusion from secure work.

Unequal employment and unemployment

Castles and Kosack also help explain why some groups may be more exposed to unemployment. If ethnic minority and migrant workers are positioned closer to the margins of the labour market, they may be more vulnerable when jobs become scarce.

Official UK data for 2022 showed that the employment rate for White people aged 16–64 was 77%, compared with 69% for people from all other ethnic groups combined. The employment rate for the combined Pakistani and Bangladeshi group was 61%, the lowest of the broad ethnic categories used in the data.

The unemployment figures show a similar pattern. In 2022, the unemployment rate was 3% for White people, compared with 6% for all other ethnic groups combined. It was 9% for the combined Pakistani and Bangladeshi group and 7% for Black people.

A Marxist would argue that these gaps are not simply the result of different levels of effort or motivation. They may reflect unequal access to secure employment, discrimination in recruitment and promotion, occupational segregation, regional inequalities and the greater likelihood of some groups being located in insecure parts of the labour market.

Pay inequality and the labour market

Castles and Kosack’s argument also links ethnic inequality to low pay. If some groups are concentrated in lower-paid sectors or less secure jobs, this can help maintain wider inequalities in income and life chances.

ONS data for 2022 found that Black, African, Caribbean and Black British employees had median gross hourly pay of £13.53, compared with £14.35 for White employees. The ONS reported that this pattern had been consistent across the period from 2012 to 2022.

The ONS also found that, after taking account of factors such as occupation, qualifications, location, age and sex, UK-born Black, African, Caribbean and Black British employees were estimated to earn 5.6% less than comparable UK-born White employees.

This is important for evaluation. Students should not treat an adjusted pay gap as simple proof of direct racism by an individual employer. However, Marxists may argue that factors such as occupation and location are themselves shaped by wider inequalities. For example, if ethnic minority workers are more likely to be concentrated in lower-paid occupations, “controlling” for occupation may hide part of the structural inequality that needs explaining.

Dividing ethnic minority workers from the White working class

A second major argument made by Castles and Kosack is that capitalism benefits when workers are divided rather than united.

They argued that migrant workers could be treated as competitors by sections of the White working class. This could encourage resentment, racism and scapegoating. Instead of workers identifying common interests against employers, they may blame one another for low wages, unemployment, housing shortages or pressure on public services.

Castles and Kosack suggested that this division weakens working-class solidarity. White workers may see migrant workers as a threat, while migrant workers may experience discrimination, poorer housing and exclusion from workplace and political power. Their original analysis argued that the division between immigrant and indigenous workers did not emerge naturally: it was reinforced by labour-market inequalities, racism and differences in status.

This remains relevant today, although it is difficult to measure directly. The UK data on insecure work, unemployment and pay show that ethnic inequalities continue to exist in the labour market. These inequalities can create the conditions in which workers are encouraged to compete with one another rather than challenge the wider structure of low pay and insecure employment.

Evaluation of Castles and Kosack

A major strength of Castles and Kosack is that they connect ethnic inequality to wider structures of power. Rather than blaming ethnic minority groups for their own disadvantage, they focus on how capitalism, labour demand and racism can shape unequal life chances.

Their work is also supported by contemporary evidence showing that foreign-born workers and several ethnic minority groups are more likely to experience insecure work, temporary employment, unemployment and lower pay. This makes their perspective useful for explaining why ethnic inequality is closely linked to employment and income.

However, their explanation can be criticised for being too economically deterministic. It can make capitalism appear to be the only cause of ethnic inequality, while overlooking the importance of culture, gender, education, immigration policy, regional differences and direct institutional racism.

It may also overgeneralise. Not all migrants are low-paid workers, and not all ethnic minority people are migrants. Some ethnic groups have high employment rates and strong representation in professional occupations. The position of a recently arrived migrant on a zero-hours contract is very different from that of a UK-born professional from an ethnic minority background.

Overall, Castles and Kosack remain highly useful because they show that ethnic inequality cannot be understood only through individual prejudice. Their Marxist approach draws attention to the relationship between ethnicity, class, insecure work and the continuing power of employers within capitalist society.

Exam-ready conclusion

Castles and Kosack argue that capitalism can use migrant labour as a flexible reserve army of labour. Ethnic minority and migrant workers may be concentrated in low-paid, insecure jobs, while racism and competition divide them from the White working class. Contemporary UK evidence on precarious work, unemployment and pay gaps gives support to this view, although students should recognise that ethnic groups have very different experiences and that not all inequality can be explained by capitalism alone.

You can download a summary of Castles and Kosack work below.