Nurse practitioner independence, health care utilization, and health outcomes.

Many states allow nurse practitioners (NPs) to practice and prescribe drugs without physician oversight, increasing the number of autonomous primary care providers. We estimate the causal impact of NP independence on population health care utilization rates and health outcomes, exploiting variation in the timing of state law passage. We find that NP independence increases the frequency of routine checkups, improves care quality, and decreases emergency room use by patients with ambulatory care sensitive conditions. These effects come from decreases in administrative costs for physicians and NPs and patients' indirect costs of accessing medical care.