Extremely Low Reciprocity and Strong Homophily in the World Largest MSM Social Network

Traditional survey-based methods are limited in the sample size and inference ability for the study of men who have sex with men (MSM), one of the most vulnerable groups at increased risk of HIV. Internet data, on the other hand, have provided publicly accessible information about such groups at unprecedented scale and resolution. Here we present statistics for the user demographics characteristics in the world's largest MSM geosocial networking application, Blued, and analyze the social network structure with 11,408,872 nodes and 838,910,078 edges extracted from user-following relationships on Blued. Network features, such as degree distribution, reciprocity, degree assortativity, homophily, and community are studied. We find that, in contrast to earlier analyses on social networks of general populations, the MSM social network is disassortative and shows extremely low reciprocity. Users in their twenties are excessively followed by users from all age groups, and network homophily for age and country are strong.