Some Interim Results from a Controlled Trial of Cost Sharing in Health Insurance

7,706 persons are participating in a controlled trial of alternative health insurance policies. Interim results indicate that persons fully covered for medical services spend around 50 percent more than similar persons insured with an income-related catastrophic plan. Full coverage leads to more people using services and increased hospital admissions. Once patients are admitted to the hospital, however, expenditure per person does not differ significantly among the experimental insurance plans. Hospital admissions for children also do not vary by insurance plan. The income-related cost sharing in the experimental plans affects expenditure by different income groups similarly, but adults' total expenditure varies more than children's. Sufficient data are not yet available on whether higher utilization by those with free care reflects overutilization, or whether lower utilization by those with income-related catastrophic coverage reflects underutilization. Both may well be true.