The Medicare Hospital Insurance (HI) Trust Fund, which funds Medicare Part A, will only be able to pay full benefits for Medicare beneficiaries until 2026, according to the 2019 annual report from the Medicare Board of Trustees. The Supplementary Medical Insurance (SMI) Trust Fund, which funds Medicare Part B and D, is expected to be adequately financed in all years, but the aging population and rising healthcare costs are projected to grow SMI costs from 2.1 percent of gross domestic product (GDP) in 2018 to approximately 3.7 percent of GDP in 2038.