Medicare spending by beneficiaries with various types of supplemental insurance.

The authors analyzed Medicare spending by elderly noninstitutionalized Medicare beneficiaries with and without supplemental insurance such as Medigap, employer-sponsored plans, and Medicaid. Use of a detailed survey of Medicare beneficiaries and their Medicare health insurance claims enabled the authors to control for health status, chronic conditions, functional limitations, and other factors that explain spending variations across supplemental insurance categories. The authors found that supplemental insurance was associated with a higher probability and level of Medicare spending, particularly for Part B services. Beneficiaries with both Medigap and employer plans had the highest levels of spending ceteris paribus, suggesting a possible moral hazard effect of insurance. Findings from this study are discussed in the context of the overall financing of health care for the elderly.