Nurse Practitioner Scope of Practice Regulations and Nurse Practitioner Supply.

Adopting full scope of practice (SOP) for nurse practitioners (NPs) is associated with improved access to care. One possible mechanism for these improvements is increased NP supply. Using county-level data, we fit cross-sectional and panel regression models to estimate the association between adopting full NP SOP and NP supply in general, and in rural and health professional shortage area-designated counties in particular. In cross-sectional analyses, we estimated positive associations between NP SOP and NP supply, though these relationships were only statistically significant when analyzing health professional shortage areas. In the panel regression models with county fixed effects, the estimated effects were attenuated toward zero and sometimes switched signs. Our findings suggest that improvements in access to care following adoption of full SOP may not be driven by increased NP supply but rather by increased capacity of NPs and physicians to provide care.