Since 2014, millions of individuals have purchased coverage through the health insurance exchanges established under Patient Protection and Affordable Care Act (PPACA). PPACA altered the individual health insurance market by setting federal standards for coverage and subsidizing exchange coverage for certain low-income individuals. In the first 5 years of exchanges, issuers have moved in and out of the market and increased premiums, but little is known about issuers' claims costs or the factors driving their business decisions. Chapter 1 examines (1) claims costs of issuers participating in exchanges, and (2) factors driving selected issuers' changes in exchange participation, premiums, and plan design. GAO reviewed data from nine issuers participating in five states, which were selected to represent a range in size, tax status, and exchange participation. During open enrollment, eligible returning consumers may re-enroll in their existing health insurance exchange plan or choose a different plan. Those who do not actively enroll in a plan may be automatically re-enrolled into a plan. Chapter 2 examines 1) the extent to which plans identified as benchmark plans remained the same plans from year to year, and how premiums for benchmark plans changed; 2) the proportion of exchange consumers who were automatically re-enrolled into the same or similar plans, and how these proportions compared to those for consumers who actively re-enrolled, and 3) the extent to which consumers' financial responsibility for premiums changed for those who were automatically re-enrolled compared to those who actively re-enrolled. Chapter 3 discussed the amendments to title XIX of the Social Security Act to ensure health insurance coverage continuity for former foster youth. Certain individuals without access to subsidized health insurance coverage may be eligible for premium tax credits, as established under the Patient Protection and Affordable Care Act (ACA; P.L. 111-148, as amended). The dollar amount of the premium credit varies from individual to individual, based on a formula specified in statute. Individuals who are eligible for the premium credit, however, generally are still required to contribute some amount toward the purchase of health insurance as described in chapter 4. During the summer of 2018, the Trump Administration issued final rules governing coverage offered through association health plans (AHPs) and short-term, limited-duration insurance. Chapter 5 describes how the Congressional Budget Office and the staff of the Joint Committee on Taxation (JCT) analyzed the new rules and determined how those rules would affect the agencies' projections of the number of people who obtain health insurance and the costs of federal subsidies for that coverage.