In the most important health insurance study ever conducted researchers at the RAND Corporation devised all experiment to address two key questions in health care financing: how much more medical care will people use if it is provided free of charge, and what are the consequences for their health? For three- or five-year periods the experiment measured both use and health outcomes in populations carefully selected to be representative of both urban and rural regions throughout the United States. Participants were enrolled in a range of insurance plans requiring different levels of copayment for medical care, from zero to 95 percent. The researchers found that in plans that reimbursed a higher proportion of the bill, patients used substantially more services - indeed, those who paid nothing used 40 percent more services than those required to pay a high deductible - but the effect on the health of the average person was negligible. In addition, participants who were assigned at random to a well-established health maintenance organization used hospitals substantially less than those in the fee-for-service system, again with no measurable effect on the health of the average person. This book collects in one place for the first time results previously dispersed through many journals over many years. Drawing comprehensive, coherent conclusions from an immense amount of data, it is destined to be a classic work serving as an invaluable reference for all those concerned with health care policy - health service researchers, policymakers in both the public and the private sectors, and students.