JAMA : the journal of the American Medical Association
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Managed care has the potential to transform fundamentally the structure and functioning of the entire health care system, including the care provided to patients who are not enrolled in managed care plans. ⋯ Managed care can have widespread effects on the health care system. Health care for individuals who are not covered by managed care organizations can be influenced by the presence of managed care. Lower expenditures in areas with high HMO market shares may indicate that traditional Medicare beneficiaries in areas with high market shares received fewer or less intensive services than traditional Medicare beneficiaries in other areas.