Homogeneity of social networks by age and marital status: A multilevel analysis of ego-centered networks

Is homogeneity in personal relationships in one trait the by-product of selection on another trait, or is it the result of direct selection on that trait? This question has often been analyzed in the context of marriage homogamy. We apply this issue to the question of whether there is selection in networks based on age on the one hand, and marital status on the other hand. The role of age has been documented before, but selection on the basis of marital status has not been documented. We analyze a representative survey containing data on contact and support networks. We use a novel analytical approach by adopting a latent class type random-effects approach to the multilevel structure of the network data which allows for simple descriptions of homogeneity in terms of odds ratio's. Our analyses show that age boundaries are strong and that they partly explain marital status boundaries. Nevertheless, even after controlling for age, we see important social boundaries between marital status groups. Moreover, we see a pattern of what we call clustered selection—the tendency of alters to be more similar to each other than one would expect from their similarity to ego.