Using Synthetic Control Method for Estimating the Effect of Nurse Practitioner Scope-of-Practice in Maryland on NP Employment

This paper uses the synthetic control method (SCM) to estimate the impact of Nurse Practitioner Scope-of-Practice (NP SOP) changes in Maryland on the number of NPs employed. Maryland’s NP SOP changes, implemented in 2011, permitted NPs to practice independently (without physician supervision) and gave them authority to write prescriptions. The results indicate that the number of NPs employed increased after the changes, relative to a synthetic control region. By 2013, the percentage of NPs employed in a practice was estimated to be about 7% higher than it would have been in the absence of SOP changes. An advantage of the SCM is that unlike the difference-in-differences method, it does not assume that the treated and control groups would follow parallel trajectories if the intervention had not taken place. From a policy perspective, because the results imply that Maryland’s regulatory change in NP SOP allowing for full practice authority had a positive effect on the number of NPs employed, similar changes in other states may be one of the levers to address the shortage of primary care providers in the United States.