Compare methods

	Religious Pluralism Index	RELTRAD Affiliation Classification
Field	Sociology Of Religion	Sociology Of Religion
Family	Process / pipeline	Process / pipeline
Year of origin	2002	2000
Originator	David Voas, Daniel V. A. Olson & Alasdair Crockett (critique); religious-economies tradition	Brian Steensland, Jerry Z. Park, Mark D. Regnerus, Lynn D. Robinson, W. Bradford Wilcox & Robert D. Woodberry
Type	Diversity/concentration index for religious composition	Classification/coding scheme for religious affiliation
Seminal source	Voas, D., Olson, D. V. A., & Crockett, A. (2002). Religious Pluralism and Participation: Why Previous Research Is Wrong. American Sociological Review, 67(2), 212-230.	Steensland, B., Park, J. Z., Regnerus, M. D., Robinson, L. D., Wilcox, W. B., & Woodberry, R. D. (2000). The Measure of American Religion: Toward Improving the State of the Art. Social Forces, 79(1), 291-318.
Aliases	Religious Diversity Index, Religious Fractionalization Index, Herfindahl Religious Concentration Index, Denominational Pluralism Index	Religious Tradition Coding, RELTRAD Scheme, Denominational Classification Scheme, Religious Affiliation Coding
Related	3	3
Summary	The religious pluralism index measures how religiously diverse a population is by computing the probability that two randomly selected people belong to different religious groups. It is the religious application of the Herfindahl-Hirschman concentration measure: one minus the sum of squared denominational shares, ranging from zero (a single dominant group) toward one (many evenly sized groups). The index became central to the sociology of religion because the religious-economies paradigm predicted that greater pluralism, by signaling competition among firms, should raise participation. David Voas, Daniel Olson, and Alasdair Crockett's 2002 American Sociological Review article showed that much of the prior literature testing this claim was undermined by a mathematical artifact linking the index to participation, making careful construction and interpretation of the index a methodological topic in its own right.	Religious affiliation classification is the task of turning hundreds of detailed denominational responses on a survey into a small, analytically useful set of religious traditions. The dominant scheme, RELTRAD, was proposed by Brian Steensland and colleagues in their 2000 Social Forces article 'The Measure of American Religion,' which criticized earlier classifications as historically and theologically incoherent and offered seven categories grounded in the development of American religious traditions: evangelical Protestant, mainline Protestant, Black Protestant, Roman Catholic, Jewish, other faiths, and no religion. By sorting respondents into traditions that share a meaningful religious heritage rather than into ad hoc groupings, RELTRAD became the standard variable through which sociologists relate religion to politics, family, and social attitudes.