The proportion of HMO enrollees in the nation’s 10 largest managed care firms rose from 46% in 1988 to 65% in 1997 and then remained at that level through the early 2000s. The proportion for 2002 (48%) is not a decline, but a change in methodology, described in the Notes below. The five largest national managed care firms in 2003 were Kaiser Foundation Health Plans, Inc.; UnitedHealth Group, Inc.; WellPoint Health Networks, Inc; Aetna Inc.; and Health Net, Inc.

Notes: InterStudy Publications revised their method of classifying HMOs according to group affiliations starting with their July 1, 2002 HMO data. Formerly, HMOs were grouped as National Managed Care Firms (NMCFs, or companies with licensed HMOs in 2 or more states with combined total HMO enrollment of 10,000 or more; plans affiliated with The Blue Cross and Blue Shield Association were included as a single group under NMCF). In 2002, InterStudy began grouping plans into National Managed Care Firms (in 2003, 25 Blues and non-Blues plans met the NMCF definition), plus 2 new groups: Intrastate Groups (12 plans in 2003 owned by a given parent or holding company but operating within only 1 state, both Blues and non-Blues) and Independent Blues Plan (23 plans in 2003 bearing the Blues brand but not part of a NMCF or Intrastate grouping). The apparent decline in the NMCF percentage for 2002 and 2003 is a result of this methodological change. HMO enrollment includes enrollees in both traditional HMOs and point-of-service (POS) plans through: group/commercial plans, Medicare, Medicaid, the Federal Employees Health Benefits Program, direct pay plans, and unidentified HMO products.

Source: Kaiser Family Foundation, Trends and Indicators in the Changing Health Care Marketplace, 2002, May 2002, Exhibit 5.11, p. 58, at http://www.kff.org/insurance/3161-index.cfm, updated with July 1 data from InterStudy Publications, The InterStudy Competitive Edge, Part II: HMO Industry Reports, 12.1 (Tables 7 and 19), 13.1 (Tables 6 and 8), and Spring 2004 (Tables 14 and 25).