The Effect of Group Size on Interfaith Marriage Among Catholics1

This article examines the relationship between the religious composition of Catholic dioceses and interfaith marriage rates among Catholics. Building on Blau's(1977) theory of intergroup relations and previous research on intermarriage, we argue that Catholics are most likely to marry outside their group when they comprise a relatively small percent of the population in their dioceses. They are most likely to marry other Catholics when they are a large percentage of the population. Research in the 1940s and 1950s supports this hypothesis, as do diocesan–level data reported in the 1960, 1965, 1970, 1975, 1980, 1985, 1990, and 1995 editions of the Official Catholic Directory . We conclude with a discussion of what these findings imply for future research on interfaith marriage among Catholics and among members of other religious groups.