This book discusses how the current health insurance market structure affects the two policy goals of expanding health insurance coverage and containing health care costs. Concerns about concentration in health insurance markets are linked to wider concerns about the cost, quality, and availability of health care. The market structure of the health insurance and hospital industries may have contributed to rising health care costs and deteriorating access to affordable health insurance and health care. Many features of the health insurance market and the ways it links to other parts of the health care system can hinder competition, lead to concentrated markets, and produce inefficient outcomes.