Mark D. Hiatt MD, Presenter: Nothing to Disclose

Given the current concern over the shortage of radiologists, it would be valuable to explore factors related to the supply of physicians. My purpose was to investigate whether a region's physician supply is related to its affluence, and how any such potential relationship has changed over the past several decades compared to R. Pearl's pioneering analysis in 1920 (Distribution of physicians in the United States, JAMA 1925; 84: 1024-8).

I used linear regression analysis to determine how the number of full-time practicing physicians in a U.S. county is related to its per capita income (PCI). The Area Resource File (ARF) of the Department of Health and Human Resources provided data for variables representing the numbers of physicians and PCI in all counties across the country in 1998. The reliability of data from the ARF (derived from the Physician Masterfiles of the American Medical Association) was assessed by computing the Pearson product-moment correlation between the number of allopathic physicians in 1998 (as contained in the Masterfiles) and number of allopathic and osteopathic physicians (who identified themselves as such in the 1990 U.S. Census). The Consumer Price Index of the U.S. Department of Labor was used to adjust PCI for inflation.

The parameter estimate for PCI was 0.0146 (p < 0.0001), reminiscent of the parameter in Pearl's study (0.0036), and the adjusted Rē was reasonably large (0.30). In determining the reliability of the data, the Pearson coefficient was 0.98 (p < 0.001).

This study shows that (1) a region's physician supply is positively related to its per capita income, and (2) this relationship, elucidated in a 1925 study, persists in more recent times. Physicians still seem, in Pearl's words, to "do business where business is good, and avoid places where it is bad."

Hiatt, M, The Relationship between Physician Supply and Per Capita Income in Counties across the United States, 1920-1998.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4415847.html