This was a good workforce study recently completed by the Macy Panel, which as part of their conclusion suggests:
Coupled with efforts to increase the number of physicians, nurse practitioners, and physician assistants in primary care, state and national legal, regulatory, and reimbursement policies should be changed to remove barriers that make it difficult for nurse practitioners and physician assistants to serve as primary care providers and leaders of patient-centered medical homes or other models of primary care delivery. All primary care providers should be held accountable for the quality and efficiency of care as measured by patient outcomes.
I like their conclusions....
The complete study can be found HERE