The Affordable Care Act (ACA), formally titled the Patient Protection and Affordable Care Act (PPACA), is a United States federal statute signed into law by President Barack Obama on 23 March 2010. It represents the most significant overhaul of the American health insurance system since the creation of Medicare and Medicaid in 1965. The law's primary mechanisms include the expansion of Medicaid eligibility, the creation of regulated insurance marketplaces, mandates and subsidies affecting individuals and employers, and a set of insurance market reforms such as guaranteed issue and prohibition on exclusions for pre-existing conditions.
Prior to the ACA's passage, an estimated 46 to 50 million Americans lacked health insurance coverage.1) The law drew heavily on earlier proposals from the Heritage Foundation and the Massachusetts health reform law signed by Governor Mitt Romney in 2006, as well as provisions advocated by consumer and labor groups. The legislation passed the Senate on 24 December 2009 and the House on 21 March 2010, with no Republican votes in either chamber. A reconciliation bill, the Health Care and Education Reconciliation Act of 2010, was signed two days later.
The ACA's core provisions include:
The ACA has faced sustained legal challenges. In NFIB v. Sebelius (2012), the Supreme Court upheld the individual mandate as a valid exercise of Congress's taxing power, while ruling that the federal government could not coerce states into Medicaid expansion by threatening to withdraw existing Medicaid funding.2) In King v. Burwell (2015), the Court upheld the availability of federal subsidies in states using the federally operated exchange.3) In California v. Texas (2021), the Court declined to strike down the remainder of the ACA after the individual mandate penalty was zeroed out, ruling on standing grounds rather than the merits.4)
Following implementation, the uninsured rate among non-elderly Americans fell from approximately 17.8% in 2010 to 10.0% by 2016.5) Debate continues among health economists over the ACA's effects on total health care costs, insurance market stability, labor markets, and the quality and accessibility of care. Proponents credit the law with expanding coverage and consumer protections; critics contend it raised premiums in certain markets, distorted labor incentives, and increased federal spending. These competing assessments are addressed on the Debate page.
Most health policy researchers agree that the ACA substantially reduced the number of uninsured Americans. There is no comparable consensus on its effects on aggregate health outcomes, long-run costs, or market structure; these remain active areas of empirical and normative dispute. See the Health Policy Consensus page for the scope and limits of existing agreement.