This defination was as follows:

These plans are defined by the NCHS as follows:

• Group HMO: "An HMO that contracts with a single multi-specialty medical group to provide care to the HMO's membership. The group practice may work exclusively with the HMO, or it may provide services to non-HMO patients as well. The HMO pays the medical group a negotiated per capita rate, which the group distributes among its physicians, usually on a salaried basis."

• Staff HMO: "A type of closed-panel HMO (where patients can receive services only through a limited number of providers) in which physicians are employees of the HMO. The providers see members in the HMO's own facilities."

• Individual Practice Association (IPA): "A type of healthcare provider organization composed of a group of independent practicing physicians who maintain their own offices and band together for the purpose of contracting their services to HMOs, PPOs (preferred provider organizations), and insurance companies. An IPA may contract with and provide services to both HMO and non-HMO plan participants."

• Med-Gap: "Private health insurance purchased to supplement Medicare."

The NCHS defines a PPO plan as:

Although the NCHS does not specifically define PFFS plans or Medicare Demonstrations, the Centers for Medicare and Medicaid Services (CMS) provides the following definitions:

• Private Fee-for-Service (PFFS): "A Private Fee-for-Service (PFFS) plan is a Medicare Advantage (MA) health plan, offered by a state licensed risk bearing entity, which has a yearly contract with the Centers for Medicare and Medicaid Services to provide beneficiaries with all their Medicare benefits plus any additional benefits the company decides to provide. One major difference between a PFFS Medicare Advantage Organization (MAO) and other MAOs is that, in most cases, people who join a PFFS MAO are not required to use a network of providers. Beneficiaries can see any provider who is eligible to receive payment from Medicare and agrees to accept payment from the PFFS MAO."

• Medicare Demonstration: "The Centers for Medicare and Medicaid Services (CMS) conducts and sponsors a number of innovative demonstration projects to test and measure the effect of potential program changes. Our demonstrations study the likely impact of new methods of service delivery, coverage of new types of service, and new payment approaches on beneficiaries, providers, health plans, states, and the Medicare Trust Funds."

In follow-up questions, interviewers recorded the names of up to four private health insurance plans. If the person was reported as covered by CHIP (beginning in 2000), by a state-sponsored health plan, or by another public program (other than Medicaid) that paid for health care, the interviewer recorded the name of that plan. The placement and wording of these questions about the names of specific government health care plans varied across years.

Persons who indicated that they were covered by Medicare (HIMCAREE) were asked their type of Medicare coverage (MCARETYP). Persons who gave any answer to this question other than just "Part A - Hospital Only," were asked whether they were "under a Medicare managed care arrangement, such as an HMO, that is, a Health Maintenance Organization?" Persons who responded affirmatively to this question were asked the question associated with MCAREHMOTYP, namely, "What is the name of the HMO?" The verbatim names given in response to this question were edited by the NCHS, and coded ("external coding") into the categories that make up MCAREHMOTYP.