How does provider supply and regulation influence health care markets? Evidence from nurse practitioners and physician assistants.

Nurse practitioners (NPs) and physician assistants (PAs) now outnumber family practice doctors in the United States and are the principal providers of primary care to many communities. Recent growth of these professions has occurred amidst considerable cross-state variation in their regulation, with some states permitting autonomous practice and others mandating extensive physician oversight. I find that expanded NP and PA supply has had minimal impact on the office-based healthcare market overall, but utilization has been modestly more responsive to supply increases in states permitting greater autonomy. Results suggest the importance of laws impacting the division of labor, not just its quantity.