To the Editor.
—In a recent article, Schwartz et al1 predict that by the year 2000 many US cities will have a shortage of most types of medical subspecialists. The authors warn that a continued expansion of the supply of physicians is necessary to meet the future demand for subspecialty care. Although the data presented in the article are of interest, we hesitate to accept them as a basis for public policy because of two potential biases in the selection of the sample population.First, the 23 states included in the sample represent only 25% of the US population, are primarily rural, and have relatively low physician-to-population ratios. As shown in the Table, the nation as a whole is preponderantly urban, with significantly more physicians per population. Indeed, the states omitted from the sample of Schwartz et al (including Washington, DC) more closely approximate national averages for the percentage