Trend lines in hmo enrollment have remained fairly steady for the last 10 years. January 2002 average enrollment (see chart, next page) shows a slight 1.7% drop from January 2001, which can be attributed to a number of factors, including the growth of PPOs and the rise in unemployment rates.

Twenty-two of the top 25 HMOs appeared in the previous year's standings, and the same eight companies remain in the top eight positions, although in a slightly different order.

Five large HMOs-all of which are based in California-continue to lead the ranks by a healthy margin and account for 17.3% of the total HMO enrollment for the 500 organizations surveyed. Of the total enrollment, 37.6% is attributed to only 5% of the companies surveyed.

The chart shows that 11 plans experienced a decrease over the year, losing 1,044,595 enrollees. Aetna plans accounted for 417,091 of those enrollees, 39.9% of the total decrease.

Top rankings are divided

almost equally among for-profit and not-for-profit companies.

Meeting Demand

Mohit Ghose, director of public relations at the American Association of Health Plans, says that HMO enrollment has remained predictable over the last 10 years because the plan offerings are designed to meet the needs of a large but specific market segment.

Employers and individuals choose their HMOs because they keep healthcare costs down while still allowing access to appropriate care and prevention programs.

"The future consumer-driven and other types of plans are all in various phases of development now," he says. "It's important in the long run to make as many options available as possible to the American consumer, and that's what the industry continues to do."

Market diversity always will be maintained because consumers demand choice, Ghose adds. Likewise, hospitals and providers will also seek to partner with plans that suit their needs best.