One study showed that, in 36.8% of trans-identifying young people’s friendship groups, the majority of members identified as trans.
Lisa Littman’s 2018 study  investigated the role of friendship groups in transgender identification, and found that the majority of the members in the friendship group became transgender-identified in 36.8% of cases – almost 2 in 5.
 Littman, L. (2018). Rapid-onset gender dysphoria in adolescents and young adults: A study of parental reports. PLOS ONE, 13 (8). [Link]