Homophily

Types of Homophily

Some of the tendency to associate with similar others is a by-product of our more limited opportunities to interact with people who are different from ourselves. This type of homophily is called induced homophily. Induced homophily refers to the tendency for interaction partners to be limited by social structure in ways that generate homogeneous groups and relations. Induced homophily stands in contrast to choice homophily, which refers to the tendency of people to choose interaction partners who are similar to themselves.

In naturally occurring groups and relationships, it often is difficult to know how much observed homogeneity occurs as a result of induced homophily and how much results from choice homophily. So, in empirical contexts, researchers often begin by taking account of baseline homophily. We can think of baseline homophily as the amount of similarity within relationships that would be expected by chance, given the choices available. For example, taking into account population information only, we would not expect any baseline homophily based on sex, since sex is an equally distributed characteristic. Baseline expectations would be that an individual would have 50% male friends and 50% female friends. Therefore, if 90% of a woman's friends are female, it indicates that something other than chance is guiding formation of her friendships. That “something” is called inbreeding homophily. Inbreeding homophily refers to any amount of homophily over and above what probability would predict based on the relative sizes of the groups in the population. In the example above, we would interpret the difference between the expected and observed rates of similarity (40%) as evidence of inbreeding homophily.

Baseline homophily reflects induced homophily. It tells us about the most basic, populationlevel constraints on our choices of interaction partners. It is more difficult to isolate choice homophily. Inbreeding homophily can reflect choice homophily, or ingroup preferences. However, inbreeding homophily can also be induced by social structures.

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