Use of out-of-plan services by Medicare members of HIP.

Use of out-of-plan services in 1972 by Medicare members of the Health Insurance Plan of Greater New York (HIP) is examined in terms of the demographic and enrollment characteristics of out-of-plan users, types of services received outside the plan, and the relationship of out-of-plan to in-plan use. Users of services outside the plan tended to be more seriously ill and more frequently hospitalized than those receiving all of their services within the plan. The costs to the SSA of providing medical care to HIP enrollees are compared with analogous costs for non-HIP beneficiaries, and the implications for the organization and financing of health services for the aged are discussed.