Access to care requires not only financial coverage, but also access to providers. While high rates of specialist physicians have been shown to be associated with higher (and perhaps unnecessary) utilization, sufficient availability of primary care physicians is essential for preventive and primary care, and, when needed, referrals to appropriate specialty care.[1,2]
Primary Care Physicians is a Ratio
Primary Care Physicians is the ratio of the population to primary care physicians. The ratio represents the number of individuals served by one physician in a county, if the population was equally distributed across physicians. For example, if a county has a population of 50,000 and has 20 primary care physicians, their ratio would be: 2,500:1. The value on the right side of the ratio is always 1 or 0; 1 indicates that there is at least one Primary Care Physician in the county, and zero indicates there are no registered Primary Care Physicians in the county.
The Method for Calculating Primary Care Physicians has Changed
Prior to the 2013 County Health Rankings, primary care physicians were defined only as M.D.s. In 2013, we included D.O.s into the definition of primary care physicians and removed obstetrics/gynecology as a primary care physician type.
Some Data are Suppressed
A missing value is reported for counties with population greater than 2,000 and 0 primary care physicians.
Although the relationship between primary care physicians and improved health outcomes is supported in the literature, this measure has a number of limitations. First, primary care physicians are classified by county, but physicians living on the edge of counties or who practice in multiple locations may see patient populations that reside in surrounding counties. Second, physicians are not the only type of primary care provider available for most patients. This measure does not include nurse practitioners, physician assistants or other practitioners available for primary care services. Finally, the way care is organized and coordinated may be just as important to health outcomes as the number of primary care physicians in an area.
Numerator (Left) Side of the Ratio
The numerator is the number of primary care physicians in a county. Primary care physicians include practicing non-federal physicians (M.D.s and D.O.s) under age 75 specializing in general practice medicine, family medicine, internal medicine, and pediatrics.
Denominator (Right) Side of Ratio
The denominator is the total county population.
Years of Data Used
Area Health Resource File/American Medical Association
The Area Health Resource File is a collection of data from more than 50 sources, including: the American Medical Association, American Hospital Association, US Census Bureau, Centers for Medicare & Medicaid Services, Bureau of Labor Statistics, and National Center for Health Statistics.
The American Medical Association maintains the Physician Masterfile, which contains information on nearly all the Doctors of Medicine and Doctors of Osteopathic Medicine in the nation.
 Steinbrook R. Easing the shortage in adult primary care -- Is it all about money? N Engl J Med. 2009;360:2696-2699.
 Baicker K, Chandra A. Medicare spending, the physician workforce, and beneficiaries' quality of care. Health Aff. April 7, 2004: w4.184-197.
 Goodman DC, Grumbach K. Does having more physicians lead to better health system performance? JAMA. 2008;299(3):335-337.