Discrimination, in its sociological meaning, involves highly complex social processes. The term derives from the Latin discriminatio, which means to perceive distinctions among phenomena or to be selective in one's judgment. Cognitive psychology retains the first of these meanings, popular usage the second. Individual behavior that limits the opportunities of a particular group is encompassed in many sociological considerations of discrimination. But exclusively individualistic approaches are too narrow for robust sociological treatment. Instead, sociologists understand discrimination not as isolated individual acts, but as a complex system of social relations that produces intergroup inequities in social outcomes.

This definitional expansion transforms "discrimination" into a truly sociological concept. But in its breadth, the sociological definition leaves room for ambiguity and controversy. Obstacles to consensus on what constitutes discrimination stem from two sources—one empirical, the other ideological and political. First, deficiencies in analysis and evidence limit our ability to trace...