Info from the report they got this from specifically related to EM
"From 2011 to 2016 indicates that over time, the proportion of ED visits where a patient is seen exclusively by a physician has been declining. 72% of ED patients were seen by a physician but not an APRN or PA, and 28% were seen by an APRN or PA (with many of these patients also seen by a physician). As a proxy for the degree to which APRNs and PAs and physicians overlap in the ED setting, we calculated the ratio of visits where an APRN or PA (and possibly a physician) saw the patient to visits where only a physician did: 2:5, or 39%. If we use it as a proxy for the degree to which APRNs and PAs offset demand for physicians across all specialty areas, the overall physician-demand projections are almost identical to physician demand under the APRN/PA High Scenario, at 834,000 physicians by 2033.
We modeled an 18% decline in emergency visits relative to the Status Quo demand projections, with a corresponding decrease in demand for emergency physicians. The modeled 18% decline starts with estimates by Truven Analytics that 71% of emergency visits by people with employer-sponsored health insurance are potentially avoidable (either by diverting the visit to an appropriate ambulatory setting or by having treated the medical condition that precipitated the visit). We assume this 71% estimate approximates potentially avoidable emergency visits for the Medicaid, Medicare, and uninsured populations. Not all potentially avoidable emergency visits can be prevented or diverted, and we modeled a 25% reduction in these visits. Thus, the 18% decline assumption reflects a 25% reduction of the 71% of potentially avoidable emergency visits. We assume each averted emergency visit would be replaced by an ambulatory visit to a physician office or outpatient or clinic setting, with ambulatory visits prorated across Primary Care and Medical Specialists (with about two-thirds of redirected visits being patients
The impact by 2033 of this scenario component is a 9,700-FTE decrease in demand for emergency physicians"