Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
We measure organizational concentration—the distribution of a patient's health care across organizations—to examine how firm boundaries affect health care efficiency. First, when patients move to regions where outpatient visits are typically concentrated within a small set of firms, their health care utilization falls. Second, for patients whose primary care providers (PCPs) exit the market, switching to a PCP with 1 standard deviation higher organizational concentration reduces utilization by 21 percent. This finding is robust to controlling for the spread of health care across providers. Increases in organizational concentration predict improvements in diabetes care and are not associated with greater use of emergency department or inpatient care.