Since its appearance in the 1930s in the form of sociometry, social network analysis (SNA) has become a major paradigm for social research in such areas as communication, organizations, and social mobility, to name but a few. It is used by researchers in a wide range of disciplines: like any mathematical approach to social research, social network analysis strips away the unique details of social situations to reveal, or model, the bare structural essentials. By doing so, it enables the researcher to identify similarities across widely disparate contexts, and so to benefit from the...