The underclass is the segment of the population that occupies the lowest possible position in a class hierarchy, below the core body of the working class.
The general idea that a class system includes a population under the working class has a long tradition in the social sciences (for example, lumpenproletariat). However, the specific term, underclass, was popularized during the last half of the 20th century, first by social scientists of American poverty, and then by American journalists.
The underclass concept has been a point of controversy among social scientists. Definitions and explanations of the underclass, as well as proposed solutions for managing or fixing the underclass problem have been highly debated.
Gunnar Myrdal is generally credited as the first proponent of the term underclass. Writing in the early 1960s on economic inequality in the U.S., Myrdal's underclass refers to a "class of unemployed, unemployables, and underemployed, who are more and more hopelessly set apart from the nation at large, and do not share in its life, its ambitions, and its achievements." However, this general conception of a class or category of people below the core of the working class has a long tradition in the social sciences, such as through the work of Henry Mayhew, whose London Labour and the London Poor sought to describe the hitherto invisible world of casual workers, prostitutes, and street-people.
The specific concept of an underclass in the U.S. underwent several transformations during the decades following Myrdal's introduction of the term. According to sociologist Herbert Gans, while Myrdal's structural conceptualization of the underclass remained relatively intact through the writings of William Julius Wilson and others, in several respects the structural definition was abandoned by many journalists and academics, and replaced with a behavioral conception of the underclass, which fuses Myrdal's term with Oscar Lewis's and others' conception of a "culture of poverty."