What is Homophily?
Homophily is the tendency for people to associate with and form connections with others who are similar to them in demographic characteristics, attitudes, values, and behaviors. It is the basic organizing principle of social networks.
How it works
McPherson, Smith-Lovin, and Cook (2001) showed that homophily operates across virtually all social dimensions: race, age, religion, education, occupation, and values. It creates networks that are more homogeneous than the population they are drawn from, which has important consequences: information circulates within similar groups (creating echo chambers), health behaviors cluster in networks (your friends’ behaviors predict yours), and opportunities flow along network lines (perpetuating inequality).
Applied example
A person’s five closest friends are likely to be similar in age, education, income, and political views. If three of them start running, the person is significantly more likely to start running too, not because of direct influence but because shared characteristics make shared behaviors likely.
Why it matters
Homophily explains why social networks amplify existing similarities rather than bridging differences, with implications for information spread, behavior diffusion, and social inequality.
