How many nurse practitioners provide primary care? It depends on how you count them.

This study compares different approaches to measuring the number of nurse practitioners (NPs) providing primary care services using data from the 2012 U.S. National Sample Survey of Nurse Practitioners, North Carolina licensing data from 2011, and a 2010 California survey of nurse practitioners and nurse midwives. Estimates of the number and share of NPs providing primary care depend on how one defines primary care. If the definition is based on the field of NP education, the estimated shares in primary care specialties are 83.5% in North Carolina and 90.7% in California; if the definition is based on current or past fields of certification, the estimated shares are 79.9% in North Carolina and 74.5% nationally. The estimated number is even smaller if one considers employment setting (58.4% in North Carolina, 66.8% in California, and 67.8% nationally), and shrinks to about half of NPs if focusing on current field of clinical specialization.