While a few independent physician-owned HMOs are winning some attention, ownership by national managed care companies accounts for a growing majority of the country's HMO enrollment, according to a recent statistical report. The figures below apply to "pure" or traditional enrollment as opposed to "open-ended" enrollment, which allows members some reimbursement for services by providers outside the HMOs.

SOURCE: INTERSTUDY PUBLICATIONS, ST. PAUL, MINN.