management at Johns Hopkins. And despite being waged at conferences and in medical journals, this is not just an academic dispute. Whatever their differences, everyone agrees that the decisions made today will have profound consequences for the future of the nation's health-care system.

In 1984, when Goodman arrived in tiny Colebrook, N.H., the physician workforce was in the midst of two seemingly contradictory trends: the number of M.D. graduates of U.S. medical schools was stagnating, but the overall physician workforce was increasing rapidly. Between 1980 and 2000, the annual number of graduates from U.S. allopathic medical schools (those that grant the M.D. degree) grew only slightly, from 15,113 to 15,674—an increase of less than 4% during a period when the nation's population grew by almost 25%. But under changes to Medicare passed in 1983, the federal government began providing additional funding to hospitals to train residents, giving teaching hospitals an incentive to create more residency positions. With the number of M.D.'s leveling off, hospitals increasingly turned to two other sources of doctors: graduates of osteopathic medical schools (those that grant the D.O. degree) and of medical schools in other countries. As a result, the total number of practicing physicians grew by almost 70% between 1980 and 2000, to more than three-quarters of a million.

By the mid-1990s, there was widespread concern that the turn of the century would bring a surplus of physicians. The Council on Graduate Medical Education (COGME), which was created by Congress in 1986 to provide advice on the training of doctors, declared in 1997 that "the United States faces an overabundance of physicians that will extend well into the next century." The organization examined the services doctors provided and used that data to project the future need for physicians. COGME concluded that the country would soon have too many doctors in most specialties.

By 2000, however, COGME and the AAMC had begun to reconsider their stances on the workforce. Soon both organizations began to warn that, if nothing changed, the nation would experience a severe shortage of physicians by 2020.

Edward Salsberg, M.P.A., the director of the AAMC's Center for Workforce Studies, explains that this change was the result of several factors. "For 1980, it made sense to slow up what was then a very rapid increase in medical school enrollment," he says. But he argues that

as managed care fell out of favor in the 1990s, it was essential to rethink what the country's needs would be in another decade or two. "When you do physician workforce planning, you really need to look 20 years out, because that's how long it takes to have any significant impact on the physician supply," he says.

Over the past few years, Salsberg and the AAMC have published a number of studies detailing the potential extent of the problem. "I personally think, and our data shows, that the shortages are going to be widespread across the full range of specialties," he says. Salsberg explains that the AAMC's conclusions rely on an analysis of demographic trends. "The aging of the U.S. population and the aging of the physician workforce are major factors," he says. For example, by 2020 the country's population is expected to reach about 335 million—an increase of 50 million from 2000. And the number of Americans over the age of 65 is expected to grow to 54 million by 2020—an increase of about 20 million from 2000. Older Americans,