Race, Ethnicity & Migration: Who Made the Categories

In the 1930 United States census, the form offered "Mexican" as a race. It was the only census that ever did. By 1940 Mexican Americans were back to being counted as white, and since 1980 the census has asked a separate question about Hispanic origin. Nobody's ancestry changed between 1930 and 1940. The category did.

That is the central lesson of this subject. Race and ethnicity are among the most consequential facts in many people's lives, and the labels people use for them are, to a large extent, the product of laws, censuses, courts and history, and they differ from country to country. Saying so is not saying that race is "not real" in its effects: a category that governs where you may live, whom you may marry or how you are treated by a police officer has real consequences whatever its origin. It is saying that to study those consequences, you first have to ask who made the categories, and for what.

This piece also covers the other half of the subject, migration: how many people actually live outside the country where they were born, where they go, what economists and sociologists have found about the effects, and how different states have answered the question of how newcomers should fit in. It is a contested field. Each position is given in terms its holders would accept, and the evidence is kept apart from the arguments.

Categories are made, not found

W. E. B. Du Bois opened The Souls of Black Folk (1903) with the line that "the problem of the twentieth century is the problem of the color-line", and spent a lifetime arguing that the line was drawn by societies, not by biology. Michael Omi and Howard Winant's Racial Formation in the United States (1986) turned that into a framework: racial categories are continually made and remade by states, social movements and everyday interaction. The census, the court and the classroom are where the line is written down.

Genetics bears on this in a particular way. In 1972 the geneticist Richard Lewontin found that about 85% of the variation in the human genes he studied lay within populations, and only a small share between continental groups. The geneticist A. W. F. Edwards replied in 2003 that Lewontin's point, while true gene by gene, does not mean that ancestry cannot be inferred: using many genes at once, people can be sorted by geographic ancestry with high accuracy. Both statements are correct. What they do not support is the nineteenth-century idea of a few discrete "races" with essences. Human variation is mostly gradual across geography. In 2023 a US National Academies report recommended that genetic research stop using race as a stand-in for genetic ancestry and describe people with measured ancestry instead. Whether "race" and "ancestry" should be kept apart in medicine and in social science is debated; the sociological claim is narrower: the social categories are not the genetic clusters.

Rules for deciding who belongs

Every classification needs a rule. Here is how a few rules from the history of the United States handle the same family. Choose each grandparent's ancestry, and see what each rule says about the grandchild. (This is historical illustration, not a way to classify anyone today.)

Without JavaScript: with one African-descended grandparent of four, the 1924 Virginia rule makes the grandchild "colored", a simple majority rule makes the grandchild "white", and the 2000-onward census lets the person tick both.

Other places use quite different rules. US states set their own rules at different times, which is why the same person could be one race in one state and another across the border. South Africa's Population Registration Act of 1950 sorted every person into White, Coloured, Bantu (later Black African) or Indian/Asian, and decided membership mostly by appearance and general acceptance in the community, with descent added in 1967; it was repealed in 1991. Brazil asks people to name their own colour, and for decades the answers have come from a wide vocabulary: when the 1976 household survey asked an open question, respondents gave more than 130 different colour terms.

One country, four ways to count

Switch between the censuses below. Each shows what the latest national count looked like, which categories were offered, and what is not asked.

Without JavaScript: US 2020, 61.6% White alone, 12.4% Black alone, 10.2% two or more races. Brazil 2022, 45.3% pardo, 43.5% white, 10.2% preto. South Africa 2022, 81.4% Black African, 8.2% Coloured, 7.3% White.

The United States has counted by race since 1790, when the first census sorted free people by sex and colour and counted enslaved people separately (under the Constitution's three-fifths clause, which counted each enslaved person as three-fifths of a person for representation). Since 1977 federal rules (OMB Directive 15) have set the standards for the whole government: race as a handful of categories, Hispanic origin as an ethnicity. The 2020 census counted 33.8 million people as multiracial, up from about 9 million in 2010, and the Census Bureau attributes most of that jump to improvements in how the questions were designed and coded, not to a sudden change in the population. In March 2024 the standards were revised: one combined question on race and ethnicity, and a new category for Middle Eastern or North African origin.

Brazil has asked about colour since the first census in 1872 (not in every census since). The answer is self-declared and the categories are colour words: branca, preta, parda, amarela and indígena. In 2022 the pardo category (roughly "brown", covering many mixed backgrounds) became the largest, at 45.3%, ahead of white at 43.5%, for the first time since 1991. Gilberto Freyre's idea of a Brazilian "racial democracy" (1930s) held that mixing had avoided American-style racism; research since the 1950s, including the UNESCO studies, documented large racial gaps in income and education. Since a 2012 law, federal universities reserve half their places for public-school graduates, with sub-quotas for Black, mixed and Indigenous students in proportion to each state's population; a 2014 law reserves 20% of federal civil-service posts for Black and mixed people. Because quota places are valuable, several universities added committees that check applicants' appearance, which is controversial in its own right. Defenders say a self-declared category invites misuse; critics say the state judging a person's looks reproduces the old classifying.

South Africa used the apartheid categories to assign where people could live, work and marry. After 1994 the same four labels were kept for a different purpose, to measure and redress disadvantage under laws such as the Employment Equity Act (1998) and broad-based black economic empowerment. The 2022 census counted about 62.0 million people. Defenders of keeping the categories say race is still the structure of disadvantage and you cannot repair what you do not measure. Critics, including some from within the redress tradition, say racial categories keep the apartheid classification alive, favour the better-off members of the groups and should give way to measures of actual disadvantage. The government's own policy debate on this is ongoing.

France has no census question on race or ethnicity. Article 1 of the 1958 Constitution commits the Republic to equality "without distinction of origin, race or religion", and the 1978 data-protection law (Informatique et Libertés) forbids, with exceptions, collecting data on racial or ethnic origin. In November 2007 the Constitutional Council struck down a clause that would have allowed studies measuring "diversity of origins" on ethnic and racial grounds. The statistical agencies instead use nationality, country of birth and the birthplace of parents; the INED/INSEE Trajectoires et Origines surveys (2008 to 2009, and 2019 to 2020) are the main source on discrimination. Supporters of the French approach argue that counting people by group creates and hardens the groups, and that the state should treat every citizen as a citizen. Critics, among them the sociologist Patrick Simon, argue that you cannot measure or prove discrimination you refuse to count, and that "colourblind" statistics leave minorities invisible. Both sides say they are defending equality. The disagreement is about whether equality requires counting.

The United Kingdom has asked an ethnic-group question in every census since 1991. Germany, with its history in mind, has been cautious about ethnic categories and uses "migration background". Mexico added a question on Afro-descendant identity in its 2020 census. India does not ask about race, and asks about caste only for Scheduled Castes and Tribes. Every one of these is a decision, and each has defenders and critics.

How many people move, and where

International migration looks vast in the news and is smaller than most people guess. The United Nations Population Division counts the migrant stock: people living in a country other than where they were born (or, for some countries, a country other than their citizenship). By its 2024 estimate there were about 304 million international migrants, about 3.7% of the world's people. In 1990 it was about 154 million, or 2.9%. In 2020, 281 million, or 3.6%. The stock includes refugees and people who moved decades ago.

Without JavaScript: 2.9% in 1990, 3.6% in 2020, 3.7% in 2024, about 1 person in 27.

The largest destination in 2024 was the United States, with more than 52 million foreign-born residents, followed by Germany (about 16.8 million), Saudi Arabia (about 13.7 million), the United Kingdom (about 11.8 million) and France (about 9.2 million). Europe and North America together host about half of all migrants. The shares of populations vary much more than the totals do, as the next tool shows. In the Gulf, foreign workers outnumber citizens: the World Bank series puts the foreign-born at 74% of the UAE in 2024. In China and India it is a fraction of one per cent.

Guessing the foreign-born share

Surveys find that people in many countries overestimate the immigrant share of their own population by a wide margin. Try it for yourself: pick a country, set your guess with the slider, then reveal.

Without JavaScript: foreign-born share in 2024 was about 74% in the UAE, 22% in Canada, 21% in Sweden, 20% in Germany, 15% in the US, 3% in Japan, under 1% in Brazil and India.

Why people move, and what the evidence says about effects

The nineteenth-century geographer E. G. Ravenstein described migration as shaped by "push" and "pull" factors; later theory added that wage gaps are not enough. Douglas Massey and colleagues argued that families send members abroad to diversify risk, that networks of earlier migrants cut the cost and risk of coming, and that migration then feeds itself. The rich-poor wage gap across a border is large; most people nonetheless stay home, because moving is costly and people prefer the places and families they know.

Specific findings are disputed. When about 125,000 Cubans arrived in Miami in the 1980 Mariel boatlift, David Card (1990) found no visible effect on wages of low-skilled workers there. George Borjas (2017) re-analysed the same events with a narrower comparison and found a large wage drop for high-school dropouts. Michael Clemens and Jennifer Hunt (2019) argued that a change in the survey's sample composition explained Borjas's result. Researchers still disagree on how large any short-term effect is on the least-skilled, though few now find large effects on the average native worker.

Assimilation, multiculturalism and the other options

The older sociology of immigration, the Chicago school (Robert Park, 1920s) and Milton Gordon (1964), expected newcomers to move steadily toward the mainstream, in language first, then jobs, then marriage. Later work found more varied paths. Alejandro Portes and Min Zhou (1993) described segmented assimilation: some immigrant children rise into the middle class, some are pushed into poor and disadvantaged neighbourhoods, and others do best by holding on to their community's networks and values. Richard Alba and Victor Nee (2003) argued instead that the mainstream itself changes, so assimilation is the blurring of boundaries and not a one-way absorption.

The empirical question under these debates is whether diversity affects trust. Robert Putnam (2007) found that, in the US, people in more diverse neighbourhoods reported lower trust, including of their own group; he argued that this was a short-run effect that societies overcome. A 2014 review by Tom van der Meer and Jochem Tolsma found a negative association in the literature that was typically weak and varied by measure. A 2006 meta-analysis of 515 studies by Thomas Pettigrew and Linda Tropp found that contact between groups under favourable conditions generally lowers prejudice. These are findings, and none of them tells a state whether to pursue assimilation or multiculturalism.

What a graduate just sees

• A census category is a decision: ask who wrote it, when, and what it was used for.
• The same family can fall into different categories under different rules, and a country's rules change within a lifetime.
• Not counting by race (France) and counting by race (the US, South Africa, Brazil) are both arguments about how to pursue equality.
• Most genetic variation lies within populations; ancestry is real, and it is not the same as race.
• About 3.7% of the world lives outside its birth country (2024), and the share depends on whether the stock or the yearly flow is meant.
• The share of foreign-born residents ranges from under 1% to three quarters of a country.
• "Immigrants lower wages" and "immigrants don't lower wages" are both too crude: effects differ by group, time and place.
• "Assimilation" and "multiculturalism" are two answers to a question every state must face; evidence about trust and contact informs each but does not decide between them.

Where it shows up next

• Stratification & Inequality (35/78): group gaps and the arithmetic of tails; this piece explains how the groups are defined.
• Gender, Family & Sexuality (35/80) and Deviance, Crime & Social Control (35/83): intersecting categories, and how policing and sentencing data are classified.
• Public Policy (35/16) and International Relations (35/14): visas, asylum law, quotas and how states bargain over migration.
• In the world: a census form, a job-application audit study, a university quota committee, a border debate, a remittance office.

If you want to go deeper

• 📘 Textbook. Michael Omi and Howard Winant, Racial Formation in the United States (Routledge, 3rd ed. 2014), the standard statement of the constructionist view; for a broader survey, the free OpenStax Introduction to Sociology (3rd ed.) chapters on race and ethnicity.
• 📘 Textbook for migration. Stephen Castles, Hein de Haas and Mark Miller, The Age of Migration (Bloomsbury/Red Globe Press, multiple editions).
• 📘 Gentler. Hein de Haas, How Migration Really Works (Viking, 2023), which tests common beliefs against data.
• 🌐 Free data. Our World in Data: Migration and the UN Population Division's International Migrant Stock tables.
• 🌐 Free course. Khan Academy: Society and culture has short lessons on race, ethnicity, migration and demographics.