The proportionate renewal of physician supply: annual kinetics expressed by a simple formula

Physician supply kinetics from education to practice to retirement fit a yearly cycle of recruitment, change, and renewal. A simple formula, a surrogate marker for semi-quantitative yearly evaluations and comparisons, is proposed. The data are published annually by the American Medical Association (AMA), and are analyzed by dividing the total by the time span in years of the designated compartment. The usual physician number is total patient care, and the average practice span is 33 years. Similarly, the average time in training of the total resident/fellow group is four years. The number available (supply) is directly compared to the annual renewal number. The same data may be used to compare states, specialties, regions census divisions, and the United States (U.S.). total over time. The proportion of annual resident/fellow supply to the annual gap in the practice category is the percent renewal; 100% suggests even; over 100%, a larger supply; and below 100% a deficit. The percent renewal, as expected, shows the magnitude of reduction following Katrina in Louisiana, even though still above 100%. The percent renewal, again as expected, shows the relative decrease in supply from 1980 to 2006 in the United States now, compared to constant yearly increases in physician numbers. The percent renewal shows a gradation in geography across the US, by half, from east to west; and a loose correlation with the physician/100,000 population ratio. The variation also is evident in the southern states, (again by half) at the extremes, and with only a loose correlation with the physicians per 100,000 population ratio. The percent renewal for specialties in the US also varies; lower for surgeons, lower in 2006 than 2003, a trend toward a stable supply when a shortage is looming. The state of Louisiana follows these trends.