Congressional Member Organizations: Their Purpose and Activities, History, and Formation [May 17, 2012] [open pdf - 412KB]
"There are 737 informal Member organizations listed in the Congressional Yellow Book or registered with the Committee on House Administration. According to self-reported information contained in the Congressional Yellow Book, the House's 652 informal Member organizations had from 1 to 215 members, with an average membership of 27, and the Senate's 85 informal Member organizations had from 1 to 75 members, with an average membership of 15. On average, House Members report membership in 38 informal Member organizations and Senators report membership in 18. Of these 737 informal organizations, 388 are registered with the Committee on House Administration as congressional Member organizations (CMO). [...] This report examines the purpose and activities of CMOs and the reasons Members form them. It also identifies and describes seven CMO types, and it provides an overview of the historical development of informal Member organizations since the first Congress, focusing on their regulation in the House by the Committee on House Oversight/Committee on House Administration, the rise and fall of legislative service organizations, and the House's decision in 1995 to issue regulations for establishing CMOs and governing their behavior. It concludes with a step-by-step guide for House Members and staff who might be interested in forming a CMO. Many of the steps in the guide may be of interest to Senators and their staff who are considering forming an informal Member group in the Senate."
CRS Report for Congress, R40683