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Physician Workforce

Economic And Demographic Trends Signal An Impending Physician Shortage

PROLOGUE: Although Medicare invests about $7 billion a year in the training of medical residents, for the past two decades Congress has never really addressed the question of how many physicians are enough to provide medical care to the U.S. population. However, the Council on Graduate Medical Education (COGME), an advisory body with little staff and limited authority, has for many years maintained that by 2000 the United States would face an overall surplus of physicians, particularly specialists, but a shortage of primary care doctors. With only a few dissenting voices along the way, this pattern of thinking has been the conventional wisdom among health workforce analysts.

Among this small cadre is Richard Cooper, a former medical school dean. Cooper and colleagues at the Medical College of Wisconsin and Temple University have developed a model that measures the adequacy of physician supply based on the growth of the nation’s economy and also on a number of factors that are changing the productivity of the average physician. They conclude that the United States is likely to experience a serious shortage of specialists in the future.

The hypothesis put forward by Cooper and colleagues comes under serious challenge in a set of invited perspectives that follow. We thought that it was important to gather a variety of views because the debate over health care workforce issues has been long neglected and deserves closer scrutiny.

Abstract

 
It is widely believed that the United States is producing too many physicians. We have approached this issue by developing a new model for workforce planning based on assessments of the macrotrends that underlie the supply and use of physician services. These trends include economic expansion, population growth, physicians’ work effort, and the provision of services by nonphysician clinicians. Contrary to earlier predictions, this model projects that the United States soon will have a shortage of physicians and that if the pace of medical education remains unchanged, the shortage will become more severe. A dialogue focused on that eventuality is imperative.

Why was the current need for physicians so underestimated? How can future requirements be more reliably discerned? And what do shortages and surpluses of physicians mean for the health care system and for the profession of medicine itself? This paper attempts to find answers to these questions in the context of the long-term trends that underlie physician supply and utilization. It leads ultimately to the question of whether it is time for the nation to begin to increase its medical training capacity to meet the demands for physicians that are evolving.

Past Predictions Of Surpluses

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Concerns about potential physician surpluses were prominent during the debate over medical school expansion in the 1960s. In 1981 the report of the Graduate Medical Education National Advisory Committee (GMENAC) gave these concerns a quantitative basis, which was reinforced by a series of studies conducted in the 1990s on behalf of the Council on Graduate Medical Education (COGME).² The message from these various studies was consistent: Surplus numbers of specialists equal to 15–30 percent of all physicians would develop by the year 2000, to be accompanied by shortages in the number of primary care physicians.

While differing in detail, these studies shared a common framework, which was based on quantifying the "tasks" (that is, physician visits and procedures) and associated "times" (expressed as full-time-equivalent, or FTE, physicians) that constituted "good" patientcare, an approach that was first developed in the 1920s by the Committee on the Costs of Medical Care (CCMC).³ This methodology was based on the assumption that more detail would lead to greater accuracy. Therefore, these studies required that physician services be disaggregated into microunits according to such factors as disease prevalence, demographic subgroups, or insurance products, a requirement that exceeded the available data and confounded the results. However, their greatest deficit was not methodological, but conceptual. It was their adoption of a social planning perspective that centered on what ought to occur, rather than an analytic approach that sought to define what most likely would occur. Nonetheless, despite challenges from some, the surpluses predicted by these studies gained wide acceptance, and they formed the theoretical basis for subsequent actions, including the termination of federal support for undergraduate medical education and a progressive decrease in support for graduate medical education.⁴

The Trend Model

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We have developed an alternative approach to physician workforce planning, based not on microanalyses of tasks and times but on macroanalyses of the long-term trends that underlie the supply and use of physician services.⁵ Four such trends were considered. First is economic expansion, the dominant factor that drives the use of health care.⁶ Second is population growth, which directly affects the need for physicians. Third is the work effort of physicians, which has been declining.⁷ And fourth are the services provided by non-physician clinicians (NPCs), which have been increasing.⁸ These four trends have been combined into a model termed the "Trend Model," which we have used to assess the adequacy of physician supply over the next twenty years.

The Trend Model differs from earlier models in several ways. First, it is a macroanalysis with relatively few data requirements, based on the notion that simpler and more aggregate models are more effective and readily reproducible. Second, it relies on long-term trends, which tend to dominate short-term fluctuations. Third, by assuming that historical trends in physician supply reflect the historical demand for physician services, it creates a conceptual link between supply and demand. This allows projections of future demand to be based on past trends and compared with separate projections of supply. Finally, while it makes assumptions about what is likely to occur, it does not base its projections on what ought to occur.

In striking contrast to earlier predictions, the Trend Model indicates that if the pace of medical education remains unchanged, the United States will soon be facing shortages of physicians and that these shortages will become progressively more severe over time. This echoes the conclusions reached by William Schwartz and colleagues, who, using a conceptually similar approach, predicted more than a decade ago that surpluses of the magnitude predicted by GMENAC and COGME for the year 2000 would not materialize.⁹

Economic Trends

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Longitudinal trends. The major trend affecting the demand for physician services is the economy. In developed countries throughout the world, health care spending has been closely tied to levels of economic development, as reflected by a country’s real (inflation-adjusted) gross domestic product (GDP) or national income.¹⁰ Since labor is the principal health care expense component, it is not surprising that growth of GDP has also correlated with growth of the health care labor force.¹¹ However, most of this growth in the work-force has involved ancillary personnel, so physicians have become a proportionately smaller component.¹² The composite result of these interrelated trends is depicted in Exhibit 1, which displays the close, long-term relationship that has existed in the United States between growth of GDP and growth of physician supply over a period of more than seventy years. The data diverged in the direction of physician undersupply in the 1960s, when most policymakers agreed that shortages were occurring, but it returned to the trend line in the 1980s following an increase in the number of physicians being trained.

View larger version (38K): [in this window] [in a new window]   EXHIBIT 1 Physician Supply And Gross Domestic Product, 1929–2000 And Projected To 2020

Cross-sectional analyses. Evidence supporting the role of economic factors in determining physician supply also emerged from cross-sectional analyses of the fifty states (Exhibit 2). Physician supply correlated with state per capita income, as had been noted earlier.¹⁶ The slopes (that is, betas) of these regressions were virtually identical at various time points over a period spanning almost thirty years. However, they were not the same for all specialties of medicine. The medical specialties (including both general and subspecialty internal medicine and pediatrics) were most responsive to income effects, while the surgical specialties were less affected, and family/general practice displayed a slightly negative relationship with per capita income. These observations not only confirm the link between economic growth and the demand for physician services but also suggest that geographic differences in physician supply are likely to persist as long as regional differences in income exist.

View larger version (16K): [in this window] [in a new window]   EXHIBIT 2 Physician Supply In States, By Major Specialty Group And State Per Capita Income, 1995

First, it is not a simple mathematical relationship that always holds true. It is a macrotrend that only applies to physicians in the aggregate over broad periods. While microturbulence, such as changes in payment schemes, governmental regulation, or the structure of health plans, may induce deviations from the trend lasting as long as five to ten years, such factors do not influence the slope of the trend, which is affected by macroeconomic dynamics.

Second, it is not a simple relationship. It results from a complex set of interrelationships that begins with increases in GDP, which (with a lag of several years) induces further demand for health services, thereby causing health care spending to rise. This leads to growth of the health care labor force, of which physicians are an important component. The fact that strong correlations exist across this entire spectrum, from GDP to physician supply, speaks to the systematic nature of the intervening steps.

Finally, the relationship between GDP and the demand for physician services does not exist in isolation. It is the consequence of countervailing societal forces that both promote and constrain utilization. For example, the perceived triumphs of technology contribute to a culture that is willing to devote more resources to health care. Similarly, although population aging does not itself cause health care spending to rise above its established trends, the elderly constitute a political force that can influence the allocation of societal resources.¹⁷ In each instance, efforts to push health care use higher are balanced by public and private "reforms" that work to constrain spending and limit access. The striking observation is that the net of these counterbalancing factors yields such stable results, infrequently allowing physician supply to deviate by more than 10 percent from its long-term relationship with GDP.

Population Trends

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Population growth is a second major factor that affects the demand for physicians. Unfortunately, mostprevious workforce analyses used unmodified population forecasts from the Census Bureau, which have proved to be low, and, therefore, the resulting projections of physicians per capita were excessively high. Indeed, this error accounts for approximately 25 percent of the physician surpluses that were previously predicted.¹⁸ To place this into perspective, the total output of ten to twelve medical schools would be required to service the population that was omitted from consideration by these earlier studies.

Using a modification of Census Bureau estimates, we have forecasted that the U.S. population will grow from 285 million in 2000 to 325 million in 2010 and that it will reach 345 million in 2020. These values are similar to those that both we and the Centers for Medicare and Medicaid Services (CMS, formerly HCFA) have used previously.¹⁹ Although 6–8 percent higher than current Census Bureau forecasts, they are within 2 percent of the projections that can be derived using data from the year 2000 census.²⁰

Physician Supply And Sufficiency Trends

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Current supply. The starting point in all workforce supply projections is an estimate of the current physician labor force. Unlike most earlier analyses, the Trend Model avoids the errors that are inherent in deciding what constitutes "one FTE physician" by basing its measures on a "head count" of all active physicians, including residents, irrespective of their level of activity. Applying this definition to data from the period of seventy years that was analyzed, physician supply increased fivefold, from 144,000 in 1929 to 772,000 in 2000.²¹ This represents more than a doubling of physicians per capita, from 119 physicians per 100,000 of population in 1929 to 270 in 2000 (Exhibit 1).

Sufficiency. To use current "head counts" of physicians for projecting future supply, one must first assess both the adequacy of physician supply and the degree to which physicians are utilized. Recent surveys of physicians and the public, combined with information on physician recruitment, yield a picture of marginal sufficiency, with a strong demand for specialists, lengthening of waiting times in many specialties, and sporadic reports of physician shortages.²²

Future supply. The method used by the Trend Model to project physician supply into the future follows the general form used by others.²³ For operational purposes, it holds inputs steady by assuming that the number of first-time, first-year residents will remain fixed at 23,000 (126 percent of U.S. medical graduates) and that 20 percent of international medical graduates (IMGs) will return to their countries of origin, as has been true over the past decade. The model also assumes that current patterns of retirement will continue.²⁴ Based on these assumptions, and using the population projections discussed above, we project that the "head count" of active physicians will increase from 772,000 (270 per 100,000 of population) in 2000 to a peak level of 887,300 (283 per 100,000 of population) in 2010 (Exhibit 1). Thereafter, the total number will continue to grow, reaching 964,700 in 2020, but the population will grow even faster, and the number of physicians per capita will actually decrease slightly, to 280 per 100,000 of population. Thus, for most of the next twenty years per capita physician supply will be essentially flat.

Physician Work Effort

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Because physician work effort is changing, these projections must be modified to reflect the existing trends. All are in the direction of reduced effort. This includes the aging of the physician workforce (with its associated decrease in hours worked), the increasing number of female physicians, the lesser work effort of physicians who are employees, the tendency of younger physicians to place a greater emphasis on personal time, the increasing frequency of early retirement, and the decreasing hours that residents are permitted to work.²⁵ Although all are important, only the first two were factored into the model, by assuming reductions of 10 percent and 20 percent, respectively, in the efforts of physicians ages 55–65 and over age 65, and a 20 percent reduction in the effort of female physicians. This resulted in a decrease in the "effective supply" of physicians by 5 percent in 2010 and 7 percent in 2020 (Exhibit 1). Because these adjustments do not include consideration of other factors that also reduce work effort, they probably overstate the amount of physician effort that will actually be available in the future.

Substitution Trends

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The final trend that we considered is the substitution of NPCs in the provision of "physician services." Until recently NPCs’ ability to substitute for physicians was limited by their licensed prerogatives and by their total numbers, but both of these limitations are diminishing.²⁶ Most NPCs now provide not only adjunctive services but also services that broadly overlap those provided by physicians, and their potential for substitution is substantial.²⁷ And their numbers are growing. By 2015 there are likely to be as many as 275,000 nurse practitioners, physician assistants, and nurse-midwives; 150,000 chiropractors and acupuncturists; and 100,000 other NPCs engaged in specific specialties, such as psychology, anesthesia, and optometry. Their combined output will be equivalent to the services of approximately 65 physicians per 100,000 of population. More than one-third of this output is in place already. Therefore, the incremental growth of NPCs over the next fifteen years was taken to be equivalent to 40 physicians per 100,000 of population (Exhibit 1), which is equal to approximately 15 percent of the physician work-force. Paradoxically, most of this growth will be concentrated in primary care, which has shown relatively stable needs, whereas the greatest growth of demand for physician services is in the non–primary care specialties, to which NPCs can be expected to contribute proportionately less.

Applying The Trend Model

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Projections. Projections based on the Trend Model build from these separate trends. On the demand side, health care spending has tended to outpace GDP by a ratio of approximately 1.5 to 1.0. If this differential continues, as has been projected, and if real per capita economic growth continues at 1.5–2.0 percent annually, as also has been projected, the fraction of GDP devoted to health care will increase from approximately 14 percent in 2000 to 18 percent in 2020.²⁸ Based on an increase in physician supply of approximately 0.75 percent for each 1 percent increase in GDP, as discussed above, the Trend Model projects a growth in the demand for physician services of approximately 1.1–1.5 percent annually (Exhibit 1), a rate of increase that is similar to the job opportunities for physicians that have been projected by the Bureau of Labor Statistics.²⁹

Comparing this growth in the demand for physician services with the number of active physicians that has been projected reveals a shortfall of substantial magnitude (Exhibit 1). This shortfall widens further when work effort is considered and demand is compared, instead, with the "effective supply" of physicians, but the incremental contributions of NPCs more than compensate for changes due to physician work effort, leaving a projected deficit in 2010 of only 50,000 physicians, less than 6 percent of the projected demand. Some of this is within the margin of error of the trends that were analyzed, and much of it could be accommodated by the elasticity of the health care labor force. However, by 2020 the deficit is projected to exceed 200,000 physicians, an amount that represents more than 20 percent of the projected demand. In percentage terms, this is greater than the shortages that existed during the 1960s.

Assumptions. To properly assess these estimates of shortages, they must be interpreted in the context of the errors and uncertainties that are inherent in the Trend Model. The assumption that the number of physicians being trained would remain constant was simply operational, since the purpose of this exercise is to determine whether that number should change. Other assumptions were in the direction of overestimating physician supply. Thus, it was assumed that the current rates of attrition would continue, although anecdotal evidence suggests that attrition is increasing. Similarly, in projecting "effective physician supply," the model assumed decrements in work effort attributable to aging and sex, but it did not consider other, less well defined factors that also have a negative impact on physician work effort. The major error in the population projections was also in the direction of overestimating per capita physician supply (by underestimating population growth), because it was assumed that the rate of immigration would not change, whereas increases seem likely. Subsequent applications of the Trend Model will have to incorporate alternative projections and assumptions as these various issues are clarified.

More ambiguity is associated with estimates of substitution, particularly since any protracted shortages of physicians are likely to cause an expansion in the autonomy and scope of practice of NPCs in those states in which these prerogatives are still limited, thereby increasing NPCs’ ability to provide "physician services." However, unless new disciplines emerge or existing disciplines vastly expand their scope of activities, substitution is ultimately limited by the range of tasks that NPCs now can reasonably assume. Thus, under most scenarios the supply of physicians plus NPCs is likely to remain relatively unchanged over the next twenty years (Exhibit 1).

The greatest uncertainty rests with the demand for physician services and with the economic growth that underlies it. While there were no indications in our analyses that the trends defining this relationship were changing, it seems inevitable that, at some point, the relative rates of economic growth and the growth of health care services will have to narrow. However, even if that occurs, or if overall economic growth slows, the inevitable divergence between an essentially flat physician supply and the rising demand that any significant economic expansion will induce predicts progressively increasing physician shortages.

The Nation’s Future Physician Supply

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These projections are made against a background of concern that health care spending is excessive and that physicians may exacerbate the problem, either by actually inducing demand or by facilitating utilization in a system in which they exert control over most expenditures, a conclusion that is not supported by contemporary data.³⁰ Among those who hold this perspective, constraining the growth of physician supply is seen as a means of limiting spending. Canada followed such a policy throughout the 1990s. Physician supply in the United States has remained lower relative to GDP than in most Organization for Economic Cooperation and Development (OECD) countries, and managed care has been used to further limit access. However, as revealed both by the backlash against managed care in the United States and by the recent recognition in both Canada and California that physician shortages are looming, such constraints inevitably conflict with long-term economic trends and with the perceptions of need that flow from them.³¹

Thus, physicians are at the nexus of a health care system that is shaped in large measure by exogenous trends. Their role is broad. It bridges an expanding universe of medical science and a long tradition of compassion and healing. But are the trends consistent with the continuation of this duality? Faced with the "taut supply" that Eli Ginzberg has advocated, it seems more likely that physicians will be drawn to those complex areas of specialty medicine that demand their attention most and that they will find it increasingly difficult to "lavishly dispense time, sympathy and understanding," as Francis Peabody urged they should.³² Patients desire the most advanced treatments, but they also seek a caring physician. Ironically, attempts to impede patients’ access to the former have had the unintended consequence of squeezing out the latter.

The sociologist Andrew Abbott has observed that "a profession whose jurisdiction is excessive must increase its productivity or expand its numbers." Conversely, "when a powerful profession ignores a potential clientele, paraprofessionals appear to provide the needed services."³³ These statements characterize the dilemma that physicians now face. Their ability to increase their productivity is limited by their declining work effort. Their ability to grow their numbers is hostage to the belief that surpluses exist. And organized medicine has embarked on a vigorous campaign to thwart expansion of the NPC disciplines.³⁴ Yet it was shortages in the past that motivated state legislatures to remove the barriers to licensure for NPCs and to enlarge their range of privileges, and it is perceived professional opportunities that stimulated the creation of new disciplines and the expansion of existing ones.

The last debate about physician shortages continued well into the 1960s. Ultimately, the Health Professions Education Assistance Act of 1963 led to a doubling of medical school slots, but it was another fifteen years before appreciably more physicians were available to the public. It is doubtful that this process could occur any more rapidly today. While the recruitment of additional IMGs could shorten the response time, the wisdom of even our current dependency on IMGs has been questioned.³⁵ If, instead, the infrastructure of medical education were expanded to alleviate just one-third of the projected shortages, more than twenty-five additional medical schools would be required over the next decade, a formidable undertaking. But to do nothing invites public discontent and forces the profession of medicine to redefine itself in an ever more narrow scientific and technological sphere while other disciplines evolve to fill important gaps. Although the path is uncertain, the choices are clear. We believe that a dialogue regarding these choices is imperative.

Editor's Notes

 
This work was supported, in part, by a grant from the Robert Wood Johnson Foundation.

NOTES

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1. For physician shortages, see J.H. Sunshine, "Employment among Recent Residency Program Graduates," Journal of the American Medical Association 281, no. 7 (1999): 611[Free Full Text]; D.C. Angus et al., "Current and Projected Workforce Requirements for Care of the Critically Ill and Patients with Pulmonary Disease," Journal of the American Medical Association 284, no. 21 (2000): 2762–2770[Abstract/Free Full Text]; California Medical Association, And Then There Were None: The Coming Physician Supply Problem (San Francisco: California Medical Association, 2001); and A. Schubert et al., "Evidence of a Current and Lasting National Anesthesia Personnel Shortfall: Scope and Implications," Mayo Clinic Proceedings 76, no. 10 (2001): 995–1010.[Medline]
2. Graduate Medical Education National Advisory Committee, Report of the Graduate Medical Education National Advisory Committee to the Secretary, Department of Health and Human Services (Washington: U.S. Department of Health and Human Services, 1981); J.P. Weiner, "Forecasting the Effects of Health Reform on U.S. Physician Workforce Requirement: Evidence from HMO Staffing Patterns," Journal of the American Medical Association 272, no. 3 (1994): 222–230[Abstract]; S. Gamliel et al., "Managed Care on the March: Will Physicians Meet the Challenge?" Health Affairs (Summer 1995): 131–142; R.M. Politzer et al., "Matching Physician Supply and Requirements: Testing Policy Recommendations," Inquiry (Summer 1996): 181–194; and L. Greenberg and J. Cultice, "Forecasting the Need for Physicians in the United States: The Health Resources and Services Administration’s Physician Requirements Model," Health Services Research 31, no. 6 (1997): 723–737. [Medline]See also the Third, Fourth, and Sixth Reports of the Council on Graduate Medical Education (Washington: U.S. Department of Health and Human Services, 1992, 1994, and 1995).
3. R.I. Lee and L.W. Jones, The Fundamentals of Good Medical Care (Chicago: University of Chicago Press, 1933).
4. Challenges to the reports from GMENAC, COGME, and related studies include U.E. Reinhardt, "The GMENAC Forecast: An Alternative View," American Journal of Public Health 71, no. 10 (1981): 1149–1157[Free Full Text]; J.E. Harris, "How Many Doctors Are Enough?" Health Affairs (Winter 1986): 74–83; W.B. Schwartz, F.A. Sloan, and D.N. Mendelson, "Why There Will Be Little or No Physician Surplus between Now and the Year 2000," New England Journal of Medicine 318, no. 14 (1988): 892–897[Abstract]; E.P. Schloss, "Beyond GMENAC—Another Physician Shortage from 2010 to 2030?" New England Journal of Medicine 318, no. 14 (1988): 920–922[Medline]; R.A. Cooper, "Seeking a Balanced Physician Workforce for the Twenty-first Century," Journal of the American Medical Association 272, no. 9 (1994): 680–687[Medline]; and R.A. Cooper, "Perspectives on the Physician Workforce to the Year 2020," Journal of the American Medical Association 274, no. 19 (1995): 1534–1543. [Abstract]Organizations endorsing these studies and their proposals included Josiah Macy Jr. Foundation, Report of the Josiah Macy Jr. Foundation for July 1, 1991, through June 30, 1992 (New York: Josiah Macy Jr. Foundation, 1992); Physician Payment Review Commission, "Graduate Medical Education Reform," in Annual Report to Congress, 1994 (Washington: PPRC, 1994), 237–263; Institute of Medicine, The Nation’s Physician Workforce: Options for Balancing Supply and Requirements (Washington: National Academy Press, 1996); and Association of American Medical Colleges, AMA, AOA, AAMC, AACOM, AAHC, NMA Consensus Statement on Physician Workforce, AAMC Advisory no. 97-9 (Washington: AAMC, 28 February 1997).
5. R.A. Cooper, "Conceptual Framework," in Evaluation of Specialty Workforce Methodologies (Washington: Council on Graduate Medical Education, DHHS, 2000), D1–D2; and R.A. Cooper, "Forecasting the Physician Workforce," in Papers and Proceedings of the Eleventh Federal Forecasters Conference (Washington: U.S. Department of Education, 2000), 87–96.
6. J.R. Seale, "A General Theory of National Expenditure on Medical Care," Lancet 2 (October 1959): 555–559[Medline]; J.P. Newhouse, "Medical Care Expenditure: A Cross-National Survey," Journal of Human Resources 12, no. 1 (1977): 115–125[Medline]; T.E. Getzen, "Forecasting Health Expenditures: Short, Medium, and Long (Long) Term," Journal of Health Care Financing 263, no. 3 (2000): 56–72; and T.E. Getzen, "Health Care Is an Individual Necessity and a National Luxury: Applying Multilevel Decision Models to the Analysis of Health Care Expenditures," Journal of Health Economics 19, no. 2 (2000): 259–270.[Medline]
7. W.B. Schwartz and D.N. Mendelson, "No Evidence of an Emerging Physician Surplus: An Analysis of Changes in Physicians’ Work Load and Income" Journal of the American Medical Association 263, no. 4 (1990): 557–560[Abstract]; P.R. Kletke, W.D. Marder, and A.B. Silberger, "The Growing Proportion of Female Physicians: Implications for the U.S. Physician Supply," American Journal of Public Health 80, no. 3 (1990): 300–403[Abstract/Free Full Text]; and P.R. Kletke, "The Projected Supply of Physicians, 1998–2020," in Physician Characteristics and Distribution in the U.S., 2000–2001 Edition, ed. T. Pasko, B. Seidman, and S. Birkhead (Chicago: American Medical Association, 2000), 361–375.
8. R.A. Cooper, P. Laud, and C.L. Dietrich, "Current and Projected Workforce of Nonphysician Clinicians," Journal of the American Medical Association 280, no. 9 (1998): 788–794[Abstract/Free Full Text]; and R.A. Cooper, T. Henderson, and C.L. Dietrich, "Roles of Nonphysician Clinicians as Autonomous Providers of Patient Care," Journal of the American Medical Association 280, no. 9 (1998): 795–802.[Abstract/Free Full Text]
9. Schwartz et al., "Why There Will Be Little or No Physician Surplus"; and Schwartz and Mendelson, "No Evidence of an Emerging Physician Surplus."
10. Getzen, "Forecasting Health Expenditures"; Newhouse, "Medical Care Expenditure"; and M. Pfaff, "Differences in Health Care Spending across Countries: Statistical Evidence," Journal of Health Politics, Policy and Law 15, no. 1 (1990): 1–67.[Medline]
11. Organization for Economic Cooperation and Development, OECD Health Data 2000: A Comparative Analysis of Twenty-nine Countries (Paris: OECD, Health Policy Unit, 2000).
12. M. Kendix and T.E. Getzen, "U.S. Health Services Employment: A Time Series Analysis," Health Economics 3, no. 3 (1994): 169–181.[Medline]
13. International data were obtained from OECD Health Data 2000. State data were from the AMA and the Bureau of Economic Analysis, U.S. Department of Commerce.
14. T.E. Getzen, "Macroeconomic Forecasting of National Health Expenditures," Advances in Health Economics and Health Services Research 11 (1990): 27–48[Medline]; and T.E. Getzen and J.P. Poullier, "International Health Spending Forecasts: Concepts and Evaluation," Social Science and Medicine 34, no. 9 (1992): 1057–1068.
15. The trend variable was adjusted for time by calculating the partial coefficient of multiple determination, which, in various analyses, ranged from 0.27 to 0.38 (p < .0001); see C.R. Rao, Linear Statistical Inference and Its Applications (New York: John Wiley and Sons, 1965), 225.
16. U.E. Reinhardt, Physician Productivity and the Demand for Health Manpower (Cambridge, Mass.: Ballinger, 1975); W.B. Schwartz et al., "The Changing Geographic Distribution of Board-Certified Physicians," New England Journal of Medicine 303, no. 18 (1980): 1032–1038[Abstract]; and R.L. Ernst and D.E. Yett, Physician Location and Specialty Choice (Ann Arbor: Health Administration Press, 1985). Correlation coefficients relating per capita income and total active physician supply ranged from 0.50 to 0.55 at six time points between 1970 and 1998.
17. T.E. Getzen, "Population Aging and the Growth of Health Expenditures," Journal of Gerontology: SocialSciences 47, no. 3 (1992): S98–S104; and T.R. Marmor, "How Not to Think about Medicare Reform," Journal of Health Politics, Policy and Law 26, no. 1 (2001): 107–117.[Medline]
18. For a critique of the use of Census Bureau projections in workforce analyses, see Cooper, "Perspectives on the Physician Workforce."
19. Ibid.; Cooper, "Seeking a Balanced Physician Workforce"; and Centers for Medicare and Medicaid Services, "National Health Expenditures Projections: 1998–2008," <www.hcfa.gov/stats/NHE-Proj/proj1998/default.htm> (15 June 2001).
20. U.S. Department of Commerce, U.S. Census Bureau, "National Population Projections," <www.census.gov/population/www/projections/natproj.html> (10 June 2001). Projections were derived using population estimates from the year 2000 census and the bureau’s prior forecasting algorithm.
21. Kletke, "The Projected Supply of Physicians"; and Bureau of Health Professions, "Total and Active Physicians and Physician-to-Population Ratios, Selected Years 1950–1997," <http://bhpr.hrsa.gov/healthworkforce/factbook.htm> (10 June 2001). For physician supply data from before 1950, see Lee and Jones, The Fundamentals of Good Medical Care; and W.H. Stewart and M. Pennell, "Health Manpower, 1930–75," Public Health Reports 75, no. 3 (1960): 274–280.
22. Physician surveys and estimates of sufficiency include Commonwealth Fund, Multinational Comparisons of Health Systems Data, 2000 (New York: Commonwealth Fund, 2000); Sunshine, "Employment among Recent Residency Program Graduates";; Angus et al., "Current and Projected Workforce Requirements";; California Medical Association, And Then There Were None; and Schubert et al., "Evidence of a Current and Lasting."; Surveys of the public include R.J. Blendon and J.M. Benson, "Americans’ Views on Health Policy: A Fifty-Year Historical Perspective," Health Affairs (Mar/Apr 2001): 33–46; and H. Smith, Critical Condition: Health Care in the 2000 Election (Princeton: Princeton Survey Research Associates, 2000). Recruitment experiences are from Merritt, Hawkins and Associates, "Summary Report: 2000 Review of Physician Recruitment Incentives," <www.merritthawkins.com/compensation/comp_index.htm> (5 January 2001).
23. Kletke, "The Projected Supply of Physicians"; Cooper, "Seeking a Balanced Physician Workforce"; and Bureau of Health Professions, Forecasting the Future Supply of Physicians: Logic and Operation of the BHPr Physician Supply Model (Rockville, Md.: DHHS, 1992).
24. Merritt, Hawkins and Associates, "Summary Report: 2000 Review of Physician 50 Years Old and Older," <www.merritthawkins.com/compensation/comp_index.htm> (15 January 2001); and C. Hogan, J.H. unshine, and B. Schepp, "Hiring of Diagnostic Radiologists in 1998," American Journal of Roentgenology 176, no. 2 (2001): 307–312.[Abstract/Free Full Text]
25. For a discussion of these factors, see Kletke et al., "The Growing Proportion of Female Physicians"; Kletke, "The Projected Supply of Physicians"; and Merritt, Hawkins, "Summary Report of Physicians 50 Years Old and Older."
26. Cooper et al., "Roles of Nonphysician Clinicians";; Cooper et al., "Current and Projected Workforce"; and E.S. Sekscenski et al., "State Practice Environments and the Supply of Physician Assistants, Nurse Practitioners, and Certified Nurse-Midwives," New England Journal of Medicine 331, no. 19 (1994): 1266–1271.[Abstract/Free Full Text]
27. M.O. Mundinger et al., "Primary Care Outcomes in Patients Treated by Nurse Practitioners or Physicians: A Randomized Trial," Journal of the American Medical Association 283, no. 1 (2000): 59–68[Abstract/Free Full Text]; S.L. Krein, "The Employment and Use of Nurse Practitioners and Physician Assistants by Rural Hospitals," Journal of Rural Health 13, no. 1 (1997): 45–58[Medline]; R.S. Hooker and L.F. McCaig, "Use of Physician Assistants and Nurse Practitioners in Primary Care, 1995–1999," Health Affairs (July/Aug 2001): 231–238; and T.H. Dial et al., "Clinical Staffing in Staff- and Group-Model HMOs," Health Affairs (Summer 1995): 168–180.
28. CMS, "National Health Expenditures Projections"; Congressional Budget Office, "The Economic Outlook," in The Budget and Economic Outlook: Fiscal Years 2001–2010, <www.cbo/showdoc.cfm?index=1824&sequence=0&from=7> (15 January 2001); and S. Heffler et al., "Health Spending Growth Up in 1999; Faster Growth Expected in the Future," Health Affairs (Mar/Apr 2001): 193–203.
29. D. Braddock, "Occupational Outlook: 1998–2008: Occupational Employment Projections to 2008," Monthly Labor Review (November 1999): 51–77.
30. E. Ginzberg, "Physician Supply Policies and Health Reform," Journal of the American Medical Association 268, no. 21 (1992): 3115–3118[Medline]; K. Grumbach and P.R. Lee, "How Many Physicians Can We Afford?" Journal of the American Medical Association 265, no. 18 (1991): 2369–2372[Abstract]; and S.A. Schroeder and L.G. Sandy, "Specialty Distribution of U.S. Physicians—The Invisible Drivers of Health Care Spending," New England Journal of Medicine 328, no. 13 (1993): 961–963. [Free Full Text]For a critique of supplied-induced demand, see S. Folland, A.C. Goodman, and M. Stano, The Economics of Healthand HealthCare (Upper Saddle River, N.J.: Prentice-Hall, 2001), 204–216.
31. P. Sullivan, "Concerns about Size of M.D. Workforce, Medicine’s Future Dominate CMA Annual Meeting," Canadian Medical Association Journal 161, no. 5 (1999): 561–562[Free Full Text]; and California Medical Association, And Then There Were None.
32. E. Ginzberg, "A Hard Look at Cost Containment," New England Journal of Medicine 316, no. 18 (1987): 1151–1154[Medline]; and F.W. Peabody, "The Care of the Patient," Journal of the American Medical Association (19 March 1927): 877–882.
33. A.D. Abbott, The System of Professions: An Essay on the Division of Expert Labor (Chicago: University of Chicago Press, 1988).
34. J. Greene, "Physicians Win Big in States over Scope-of-Practice Issues," American Medical News, 2 July 2001, 1–2.
35. F. Mullan, "The Case for More U.S. Medical Students," New England Journal of Medicine 343, no. 3 (2000): 213–217.[Free Full Text]

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