According to the CBO, the federal government spent less on Medicare and Medicaid over the last decade than expected and this is expected to continue.
Medicare's lower projected spending was driven by more drugs becoming generics and fewer brand-name drugs.
Medicaid's lower projected spending was driven in part by lower costs for long-term services and supports (daily care for individuals with disabilities/etc.) from fewer individuals than expected, a shift away from institutional settings, and the rise of managed care organizations.