of faculty had grown by more than 50 percent, to nearly 4,200, and it more than doubled again during the next decade, to reach 11,300 by 1960 (Burke, 1992). This rapid rate of growth was fueled by several policy changes by the federal government, most notably the surge in federal research monies flowing to universities, the government's decision to push for training of more doctors, and the concomitant funding made available for building new medical school facilities throughout the 1960s (Ahrens, 1992; Institute of Medicine, 1990). The number of medical schools grew to 95 by 1969 and to 127 by 1982. There has been only one closure, leaving the present total of 126 medical schools of which 74 are publicly supported institutions and 53 are private (Ahrens, 1992).
Obtaining demographic data on the subset of academic faculty performing patient-oriented clinical research is hampered by the lack of a database for recording these data, the heterogeneity of the disciplines engaged in clinical research, and the inability to separate clinical investigator faculty from those with predominantly laboratory-based research or clinical care responsibilities. Furthermore, many faculty may be involved in more than one of these areas, possibly both laboratory and human research or human research and patient care. Unlike the Doctorate Record File database maintained by the National Research Council, which records the doctorates conferred on all graduates of U.S. institutions and gives some indication of the talent pool for biomedical research, comparable listings for medical or dental school graduates do not provide insight into the potential researcher pool in these professions (National Research Council, 1989a). Also, Vaitukaitis has shown that almost half of all grant awards to investigators indicating the use of humans or human materials are to Ph.D.s (Vaitukaitis, 1991). Because clinicians are trained primarily to provide health care, they have alternate career options available if research pathways appear unappealing because of difficulties in funding or other reasons. In addition, there is no way to quantify the reserve pool of clinical investigator talent—the number of adequately trained clinicians who might apply for research funding if the chances for garnering funds were somewhat better.
To gain a clearer understanding of the physician-investigator workforce, it is useful to look at the total pool of U.S. physicians and its subsets, particularly those on the faculties of medical schools, where the majority of academically based clinical investigators are believed to be employed. According to the American Medical Association (AMA) Physician Masterfile, there were more than 615,000 M.D.s in the United States in 1990, of whom about 90 percent were active in medical practice (American Medical Association, 1992). What is very striking is that the number of women physicians has quadrupled since 1970, from 25,401 (7.6 percent of the 334,038 physicians in 1970) to 104,194 (16.9