The meaning of heterogeneity: an introduction.

In response to widespread, popular perceptions of homogeneity among elderly persons, gerontologists are quick to point out that the older population comprises extensive variation, perhaps more so than any other age group. Despite the vociferous calls for the public to become more aware of differences among older persons, there are relatively few empirical studies that report measures of heterogeneity, dispersion, variation, or diversity. The struggle between two competing goals of inquiry — identifying and explaining central tendencies or commonalities versus identifying and explaining systematic variations — seems to end more often than not with the researchers focusing on means or averages and giving short shrift to the range of responses or outcomes (Nelson & Dannefer, 1992). The purpose of this symposium is not to document age heterogeneity empirically, but rather to develop theoretical understandings of the mechanisms that contribute to heterogeneity among aged persons. The three authors begin from sociological perspectives, but then call upon theories and research from other disciplines to gain a deeper and fuller understanding of the structures and processes underlying heterogeneity. Toni Calasanti ("Incorporating Diversity: Meaning, Levels of Research, and Implications for Theory") distinguishes diversity from heterogeneity, terms often used interchangeably, and then explores the significance of diversity for gerontological research and theory. Drawing upon feminist theories, theories of political economy, and empirical examples from work and retirement, she shows how diversity "provides a framework that is built upon the experiences of a particular group or groups as they