Robert C. Bowman, M.D.
New methods are needed that capture physician distribution. Current methods are largely a matter of geography. Physician distributions are related to population distributions, but physician distributions are more strongly related to other factors such as concentrations of physicians, health resources, income, health care coverage, and professionals.
Major medical centers are one way to express physician concentrations. The author used zip coding databases and captured physician distributions by practice zip codes. In addition to concentrations of physicians, the database included zip code data involving poverty levels, geographic definitions, and types of locations.
For most purposes in this web site, major medical centers are defined as medical school zip codes or zip codes with 75 or more physicians. An additional category of Super Center or zip codes of 200 or more physicians at a zip code is also used. About 46% of US physicians are found in Super Centers and another 24% are found in zips with 75 - 200 physicians for a total of 70% with major medical center location. Medical school zip codes shared the same characteristics as major medical center zip codes. Medical school zip codes were determined using zip code lists of medical schools, internal medicine departments, family medicine departments, and Masterfile listings of concentrations of physicians in teaching, research, or residency.
Underserved locations were determined by high levels of poverty or by zip codes known to have federal sites or programs. Zip codes with 19% or more in poverty or zip codes with a Community Health Center or National Health Service Corps or whole county primary care shortage areas were considered underserved, but only if they were not a major medical center and had more than 14% in poverty. Some sites did not have the higher levels of poverty consistently linked to underservice. When poverty levels dipped below 14% at a zip code or when there were too many physicians at a zip code, even designated sites were not considered underserved. In the following table, the various physician locations and the zip code poverty levels, physician ratios, and physician to poverty population ratios are considered.
Physician Distribution Categorization
|
|
Major Medical Center |
Served |
Underserved |
|
|
|||
|
|
Super (200+) |
Typical (75-199) |
Urban |
Rural |
Urban |
Rural |
Military |
Total |
|
Practice Zip Codes |
1,117 |
2,231 |
16,020 |
9,312 |
3,955 |
9,391 |
1,816 |
43,842 |
|
US Pop 2000 (millions) |
32.021 |
61.434 |
96.230 |
23.887 |
34.556 |
23.705 |
1.949 |
273.8 |
|
% By Location |
11.7% |
22.4% |
35.1% |
8.7% |
12.6% |
8.7% |
0.7% |
1 |
|
Per Square Mile |
1769.83 |
689.56 |
239.20 |
30.87 |
232.77 |
18.31 |
122.99 |
99.8 |
|
US Pop Poverty (millions) |
3.895 |
6.508 |
7.738 |
2.485 |
8.425 |
4.636 |
0.195 |
33.88 |
|
% By Location |
11.5% |
19.2% |
22.8% |
7.3% |
24.9% |
13.7% |
0.6% |
100% |
|
Per Square Mile |
215.275 |
73.047 |
19.234 |
3.212 |
56.752 |
3.581 |
12.301 |
12.36 |
|
Poverty Concentration |
12.2% |
10.6% |
8.0% |
10.4% |
24.4% |
19.6% |
10.0% |
12.4% |
|
Poverty to Pop Index |
0.983 |
0.856 |
0.650 |
0.841 |
1.970 |
1.581 |
0.808 |
1 |
|
Physician to Pop Index |
3.643 |
1.295 |
0.489 |
0.428 |
0.290 |
0.347 |
1.029 |
1 |
|
Physicians Per Sq Mile |
19.145 |
2.651 |
0.348 |
0.039 |
0.200 |
0.019 |
0.376 |
0.297 |
|
Active Physicians Per 100,000 Population |
1081.76 |
384.45 |
145.28 |
127.07 |
86.12 |
103.19 |
305.50 |
296.97 |
|
All Active Physicians (Total Minus Retired) |
346389 |
236186 |
139807 |
30354 |
29760 |
24460 |
5954 |
813,099 |
|
42.6% |
29.0% |
17.2% |
3.7% |
3.7% |
3.0% |
0.7% |
100.00% |
|
|
Recent Grads 1987-2000 |
46.1% |
26.5% |
14.5% |
3.6% |
4.2% |
3.3% |
1.7% |
100.0% |
|
Recent Grads 1987-2000, Classified, Not Residents |
41.4% |
28.6% |
15.5% |
4.3% |
4.5% |
3.7% |
1.9% |
100.0% |
|
% FPGP at Location |
7.7% |
15.2% |
25.9% |
38.6% |
23.8% |
36.9% |
21.6% |
16.1% |
|
FPGP |
19.8% |
27.1% |
25.0% |
10.2% |
6.6% |
8.6% |
2.6% |
100.0% |
|
Not FPGP |
45.6% |
28.9% |
13.7% |
3.1% |
4.1% |
2.8% |
1.8% |
100.0% |
|
FPGP / Not FPGP Ratio |
0.43 |
0.94 |
1.83 |
3.29 |
1.63 |
3.05 |
1.44 |
1.00 |
Physician concentrations varied from 1082 physicians per 100,000 or 3.6 times the average distribution of 297 to levels one-third of the average concentration in both types of rural areas. Physicians and population were concentrated in the super and typical major medical center locations with 71.6% of physicians and 34% of the population.
Poverty population numbers were equally divided across the three major divisions – major medical center, served, and underserved. Underserved areas had the greatest concentrations of poverty with two to three times the level of major medical center or served areas.
In separate comparisons, the two subgroups (designation subgroup and poverty subgroup) of underserved location had comparable numbers of physicians, physician ratios, population, and poverty population. Even the three different shortage designation types had similar low concentrations. Underserved areas were the best indication of inequity in physician distribution with 21.6% of the population and only 6.7% of the physicians.
The rural areas and the urban underserved areas face greater concentrations of poverty, lower income levels, decreased economic support, and fewer health resources in addition to geographic barriers and the factors of distance from decision-makers. Even the urban served areas do not fare as well, perhaps an indication of the dominance of nearby major medical center locations.
The contributions of family physicians are readily seen with fewer found in the super centers and average or above concentrations in all other locations. Family physicians are much more likely to be found in locations outside of major medical centers compared to other physicians. Only the Super Medical Center location has less than the national average for family physician concentration. With family medicine “excluded” from super center locations with 46% of physicians, family physicians can distribute at greater levels to all other locations. This means that family practice distributions match up closest to population and poverty distributions. About half of family physicians are available to distribute to the 66% of the population beyond major medical center locations. With any specialization beyond family medicine, physicians are limited to major medical center locations. No specialty distributes with the 1.6 – 3 times multiplier effect seen in family medicine. This effect remains when controlling for school or type of school of graduation, physician origin (rural or underserved origin), or state location. Origins multiply distribution above national averages by 2 – 3 times and the same 2 – 3 times multiplier is found for family medicine. The top levels of distribution in the nation are found with family medicine choice plus rural, lower income, or underserved origins (or both) at 4 – 6 times national averages.
The Masterfile contains a variety of zip codes for use in physician location determinations. Comparisons can be useful in understanding the consistency of coding. The OfficeMax software selects the most likely practice location from the available choices for a physician. A different method prioritizes practice zip codes then uses home zip codes for physicians with missing data. Other methods exclude inactive and retired physicians. Professional zip codes are available for most active physicians and can also indicate distributions of this subset.
Comparisons of Available Zip Code Choices
|
|
Medical Center |
Served |
Underserved |
Military |
Total |
|||
|
|
Super |
Major |
Urban |
Rural |
Urban |
Rural |
|
|
|
All Grads 1987 – 2000 Office Max |
145,934 |
84,080 |
41,537 |
15,818 |
13,431 |
10,186 |
5,525 |
316,511 |
|
46.1% |
26.6% |
13.1% |
5.0% |
4.2% |
3.2% |
1.7% |
100.0% |
|
|
All Physicians Including Inactive and Retired |
372,577 |
261,773 |
145,155 |
51,778 |
33,449 |
28,109 |
6,385 |
899,226 |
|
41.4% |
29.1% |
16.1% |
5.8% |
3.7% |
3.1% |
0.7% |
100.0% |
|
|
All Grads 1971 - 2000 Office Then Home Codes |
223,143 |
151,897 |
83,606 |
29,660 |
16,910 |
14,692 |
4,643 |
524,551 |
|
42.5% |
29.0% |
15.9% |
5.7% |
3.2% |
2.8% |
0.9% |
100.0% |
|
|
All Grads since 1971 Professional Zip Codes |
172,988 |
102,830 |
46,530 |
21,421 |
17,394 |
14,015 |
3,718 |
378,896 |
|
45.7% |
27.1% |
12.3% |
5.7% |
4.6% |
3.7% |
1.0% |
100.0% |
|
|
All Grads since 1971 Home Zips |
198,743 |
158,226 |
97,959 |
30,057 |
15,930 |
13,891 |
2,648 |
517,454 |
|
38.4% |
30.6% |
18.9% |
5.8% |
3.1% |
2.7% |
0.5% |
100.0% |
|
|
Active Physicians Since 1940 Office Then Home |
281,324 |
197,154 |
113,193 |
42,335 |
23,257 |
21,307 |
5,536 |
684,106 |
|
41.1% |
28.8% |
16.5% |
6.2% |
3.4% |
3.1% |
0.8% |
100.0% |
|
|
Retired Only |
25,999 |
25,587 |
18,890 |
7,891 |
3,693 |
3,717 |
433 |
86,210 |
|
30.2% |
29.7% |
21.9% |
9.2% |
4.3% |
4.3% |
0.5% |
100.0% |
|
The basic physician concentrations remain despite the use of different zip code types. Selection of different class year groups and different practice locations does involve some slight variations. Professional zip codes maximize Super Center and underserved location, an apparent improvement in resolution or validity when the data contains a more specific zip code. Home zip codes minimized both major medical center and underserved location. Significant levels of physician home and retired zip codes appear to be found in the urban served category. The pure retired group confirmed greater urban served location and also paradoxically the greatest level of underserved location. The pattern of physician retirement to rural and lower cost locations has been noted by Ricketts at the Sheps Center in North Carolina. Retirement migrations are likely to involve a move from the highest cost to lower or lowest cost locations.
Five Periods of Health Policy and Physician Career Choice
Physician Distribution in the United States