Sociology evolved as an academic response to the challenges of modernity, such as industrialization, urbanization, secularization, and a perceived process of enveloping rationalization. The field generally concerns the social rules and processes that bind and separate people not only as individuals, but as members of associations, groups, communities and institutions, and includes the examination of the organization and development of human social life. The sociological field of interest ranges from the analysis of short contacts between anonymous individuals on the street to the study of global social processes. In the terms of sociologists Peter L. Berger and Thomas Luckmann, social scientists seek an understanding of the "Social Construction of Reality". Most sociologists work in one or more subfields. One useful way to describe the discipline is as a cluster of sub-fields that examine different dimensions of society. For example, social stratification studies inequality and class structure; demography studies changes in a population size or type; criminology examines criminal behaviour and deviance; and political sociology studies the interaction between society and state.