In 1903 W. E. B. Du Bois opened The Souls of Black Folk with a prediction: "The problem of the twentieth century is the problem of the color-line." The century that followed proved him right in many countries. This level looks at how sociologists study race and ethnicity, and then at the family, the institution where most people first learn who they are.

Race as a social construction

Sociologists describe race as socially constructed. This does not mean race is imaginary or unimportant. It means that the categories of race and their meanings are made and changed by societies, not fixed by biology. Human genetic variation is real, but most of it lies within so-called racial groups rather than between them, and the lines between groups are drawn differently in different places. The racial categories on the United States census have changed in nearly every census since 1790. Groups such as Irish and Italian immigrants were once widely treated as not fully white in America, and later were. Ethnicity, by contrast, refers to shared cultural heritage: language, ancestry, religion and customs.

Socially constructed categories still have hard consequences. In 1928 the sociologists W. I. Thomas and Dorothy Swaine Thomas wrote: "If men define situations as real, they are real in their consequences." This idea, known as the Thomas theorem, holds that situations people define as real have real consequences. If employers, lenders and police treat a category of people as dangerous, that belief shapes jobs, homes and lives, whatever its truth.

Double consciousness

Du Bois also described the inner experience of living under such definitions. He wrote of "this double-consciousness, this sense of always looking at one's self through the eyes of others, of measuring one's soul by the tape of a world that looks on in amused contempt and pity." Double consciousness, in Du Bois's sense, is seeing oneself through the eyes of a society that looks down on one's group, while also knowing oneself from within. The idea links to Cooley's looking-glass self, with a crucial difference: the mirror is distorted by prejudice.

Institutional discrimination

Prejudice is an attitude and discrimination is an action. Sociologists add a third idea. Institutional discrimination is unequal treatment built into the normal rules and practices of institutions, so that it can continue even when no individual intends harm. A clear historical case is redlining. In the 1930s the federally sponsored Home Owners' Loan Corporation drew color-coded maps of American cities, and redlining maps marked Black and immigrant neighborhoods as risky for loans, shading them red. Lenders and federal mortgage programs followed similar rules for decades. Because home equity is the main form of wealth for most families, the effects passed to children and grandchildren long after the maps were retired.

How can researchers detect discrimination today? One method is the audit study. In a well-known experiment published in 2004, economists Marianne Bertrand and Sendhil Mullainathan mailed fictitious résumés to employers in Boston and Chicago, identical except for names. Résumés with white-sounding names drew about 50 percent more callbacks than those with Black-sounding names. Because only the name differed, the gap pointed to discrimination rather than qualifications.

The family

Every society has some form of family, but its shape varies widely. A nuclear family consists of parents and their children. An extended family includes parents and children plus other relatives such as grandparents, aunts or cousins, often living together or close by. For most of history and in much of the world today, extended families have been the norm. Families perform several functions: raising and socializing children, sharing economic resources, caring for the sick and old, and giving emotional support.

Family life in wealthy countries has changed fast. People marry later: in the United States the typical age at first marriage is now around thirty for men and twenty-eight for women, compared with the early twenties in 1960. More couples live together without marrying, more people live alone, and families formed through remarriage, adoption and same-sex marriage are more visible. Gender roles within families have shifted as well. Sociologists debate whether these changes weaken the family or simply show it adapting, as it always has.

Worked example: a house in 1950

In 1950 two veterans with similar jobs try to buy homes in the same city. One is white and buys in a new suburb with a low-interest, federally backed loan. The other is Black. His neighborhood is shaded red on the lending maps, and suburban developers refuse to sell to him. He rents. Seventy years later, the first veteran's grandchildren have inherited a house worth several hundred thousand dollars; the second veteran's grandchildren have inherited little. No one in the present generation needs to hold any prejudice for the gap to persist. The Thomas theorem explains how a belief about risk became a real difference in wealth, and the idea of institutional discrimination explains why it outlasted the people who drew the maps.