Michael Geruso Publications

This paper examines the effects of privatizing social health insurance. We exploit a natural experiment in Medicaid, wherein nearly 100,000 enrollees were randomly assigned between a publicly operated fee-for-service system and private managed care. Managed care reduced costs by 5.6 percent via cost-effective substitutions among prescription drugs and via lower prices for outpatient services. We present evidence that pharmacy utilization management was the key mechanism reducing overuse and encouraging substitution to lower-cost drugs without decreasing observed quality. In contrast, privatizing medical benefits led to only modest savings and was associated with decreased health care quality and consumer satisfaction.

Exploiting the random assignment of Medicaid beneficiaries to managed care plans, we find substantial plan-specific spending effects despite plans having identical cost sharing. Enrollment in the lowest-spending plan reduces spending by at least 25 percent—primarily through quantity reductions—relative to enrollment in the highest-spending plan. Rather than reducing "wasteful" spending, lower-spending plans broadly reduce medical service provision—including the provision of low-cost, high-value care—and worsen beneficiary satisfaction and health. Consumer demand follows spending: a 10 percent increase in plan-specific spending is associated with a 40 percent increase in market share. These facts have implications for the government's contracting problem and program cost growth.