ships between patients, health plans, and providers. Because of these changes, such classifications as Health Maintenance Organization, Independent Practice Association, Preferred Provider Organization, and fee-for-service no longer adequately distinguish among types of health care plans.

Finally, the Health Insurance Portability and Accountability Act of 1996 (HIPAA) mandates several changes in the private health insurance market that may affect participation and costs for Medicaid and other social welfare programs. For example, HIPAA extends the portability of health insurance coverage for workers who change jobs, and it limits restrictions on pre-existing conditions for new coverage. (For a more detailed description of the changing public and private sector health care systems and the implications for the adequacy of existing data, see Harvey, 1996.)