Introduction: The geographic distribution of physicians in the United States of America has been often described as unbalanced or maldistributed. There is much in the literature on the regional distribution of physicians but far less is written about their pattern of movement. This study aimed to examine the geographic transition of physicians at two points in time (1981 and 2003), in and out the four US census regions (Northeast, Midwest, South, and West).
Methods: We identified 83 383 non-federal clinically active primary care physicians (CAPCP) who were clinically active both in 1981 and in 2003 as registered in the American Medical Association Physician Masterfiles. The main variable was the migration status observed between 1981 and 2003, and they were categorized into three groups: (1) non-migrants (same county of practice); (2) internal migrants (different counties of practice, same region); or (3) external migrants (different regions of practice). Covariables were gender and age for the CAPCP, and the percentage of non-whites in the population, the mean per capita income of the population, the ratio of primary care physicians and the ratio of hospital beds per 1000 inhabitants, as well as the rural/urban status for the county of practice in 1981 (large metropolitan area, small metropolitan area, or non-adjacent).
Results: Overall, 13.2 % of CAPCP moved from one region to another between 1981 and 2003. Women and young CAPCPs were more prone to migrate during their career. Proportionally, a greater outflow of the 1981 workforce is observed for the Northeast and Midwest regions with 16% and 18%, respectively, compared with 10% for both the West and South regions. When taking into account the total flow (in and out) for each region, the West and the South 'benefited' from CAPCPs' migration, with respectively a 1.10 and 1.07 increase in 2003 when compared with 1981; while the Midwest and the Northeast regions ended with a 0.90 and 0.92 decrease in 2003. Both logistic regression and regression-tree analyses show that a physician's age is the most important covariate for all regions, with CAPCPs in their 30s being the most prone to migrate outside the region, whereas gender is a significant factor only in older CAPCPs in the Midwest and South region. The percentage of non-white population in the county of origin is also a significant covariate for all regions.
Conclusions: This study looked at the net movement of clinically active primary care physicians across census regions between 1981 and 2003, and underscores the importance of performing specific regional analysis in large countries where socio-demographical and geographical heterogeneities can be observed. Overall, 13.2% CAPCP moved from one region to another over the 22 year period: the South and West regions benefited while the Midwest region was disadvantaged by the migration flow. Age is the major determinant of migrant CAPCP. Logistic and regression tree models also show that percentage of non-white population of the county of origin is a major determinant of migration.