Ronald L. Breiger is Professor of Sociology at the University of Arizona, where he is also affi liated with the Graduate Interdisciplinary Program in Statistics and the School of Government and Public Policy. His research interests include social networks, stratiﬁ cation, mathematical models, theory and measurement issues in cultural and institutional analysis. He has recently published in Sociological Methods & Research, Research in the Sociology of Organizations, Poetics, Lecture Notes in Computer Science and the Annual Review of Sociology. With Ray-May Hsung and Nan Lin, he is a coeditor of Contexts of Social Capital: Social Networks in Markets, Communities, and Families (Routledge, paperback ed. 2012).