Policy Matters: 10-Year Trends in Supply of Anesthesiologists

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April 1, 2014 Volume 78, Number 4
Policy Matters: 10-Year Trends in Supply of Anesthesiologists Thomas R. Miller, Ph.D., M.B.A.
Nicholas Halzack, M.P.H.

In the August 2013 “Policy Matters,” we described the importance and challenges of workforce analysis and provided physician workforce data from the American Medical Association (AMA) and the National Plan and Provider Enumeration System, with the assurance of more data to follow in the future. In this “Policy Matters,” we examine 10-year trends (2003-12) in the supply of anesthesiologists based on AMA data.1

We focus our analysis on the number of anesthesiologists in the 50 U.S. states and the District of Columbia involved in “patient care” activity, rather than those primarily involved in administrative activities, medical education, medical research or other activities. In 2012, there were 45,357 anesthesiologists (98 percent of all anesthesiologists) involved in patient care activity. Anesthesiologists represented 5.8 percent of all physicians in patient care activity in 2012.


Exhibit 1 presents the number and growth rate of anesthesiologists between 2003 and 2012 along with the U.S. population growth. The physician anesthesiologist workforce increased 16.2 percent over this 10-year period, compared to a 13.4 percent increase in the overall physician workforce. During this time period, the number of primary care physicians, gastroenterologists and surgeons increased 6.6, 20.2 and 4.7 percent, respectively.


Exhibit 1


We examined changes in the supply of nurse anesthetists using the Medicare 5 percent beneficiary sample claims data. We compared growth rates in the number of physician anesthesiologists and nurse anesthetists with Medicare claims between 2009 and 2012. Over this time period, the number of nurse anesthetists increased almost three times faster (14.7 percent) than the number of anesthesiologists (4.4 percent). Also indicative of the increase in the supply of nurse anesthetists is the growing number of education programs and graduates. Between 2001 and 2011, the number of graduating nurse anesthetists more than doubled (from 1,159 to 2,447).3 Although we were unable to obtain national data on the number of practicing nurse anesthetists each year between 2003 and 2012, based on various publicly available sources we estimate an increase of 50-75 percent.


Physician supply typically is examined relative to the population that drives the demand for health care services. We compared 10-year changes in the ratio of the number of anesthesiologists to population (ApPR) by state (Exhibit 2).Between 2003 and 2012, the ApPR in the U.S. grew 7.4 percent. At the state level, the percentage change ranged from a 30 percent increase in the District of Columbia to a 16 percent decrease in Idaho.


Exhibit 2


Population change is not the only driver of a change in the supply of physicians. For anesthesiologists, relative changes in the number of surgeons, gastroenterologists and other physicians also impact the supply of anesthesiologists over the long term. Using state-level physician supply data for 2003 and 2012, we ran a multivariate regression to predict changes in the number of anesthesiologists over the 10 years (Exhibit 3). Changes in the number of gastroenterologists and in the number of surgeons within a state had a relatively large and significant effect on the changes in the number of anesthesiologists. The number of anesthesiologists in the base year (2003) and the change in the number of other physicians also were significant predictive variables, although the effect sizes were relatively small. The model accounts for 95 percent of the variation in the change in the number of anesthesiologists across states. We ran another model that included changes in state population; however, it did not have a significant independent effect. Changes in the demand for non-procedural-related anesthesia services are likely also to be important workforce considerations, but relevant data were not available to include in this analysis.


Exhibit 3


These simple trends and analysis raise several complicated questions, such as:

• What other environmental or cultural factors (e.g., growth in physician groups, average work hours, technology and labor substitutes) play a role in the changes in physician supply?

• Are we moving toward equilibrium in the demand for and supply of physician anesthesiologists, or away from equilibrium?

• How much do state-level policies influence workforce changes?


ASA engaged the RAND Corporation to conduct an extensive anesthesiology workforce survey and analysis. The study represents an update to a RAND Corporation report published in 2010.4 The final report and any articles associated with the most recent study will be available later this year, and ASA members will be notified when the report is released.


ASA’s Department of Health Policy Research continues to build and maintain an anesthesia workforce database, and we encourage ASA component societies to share local and state-level manpower data with us. These data help ASA develop a more complete and accurate understanding of the anesthesia workforce and related issues along with state and national health policy implications.

Thomas R. Miller, Ph.D., M.B.A. is ASA Director of Health Policy Research.


Nicholas Halzack, M.P.H. is ASA Health Policy Research Analyst.



1. Division of Survey & Data Resources, American Medical Association. Physician Characteristics and Distribution in the U.S. [2005-2014]. Chicago: AMA; [2005-2014].

2. Population estimates: historical data [2003-2012 data]. U.S. Census Bureau website. http://www.census.gov/popest/data/historical/index.html. Accessed January 27, 2014.

3. Health Resources and Services Administration, Bureau of Health Professions, National Center for Health Workforce Analysis. The U.S. Nursing Workforce: Trends in Supply and Education. Washington, DC: HRSA, Bureau of Health Professions; 2013:51.

4. Daugherty L, Fonseca R, Kumar KB, Michaud PC; RAND Health. An Analysis of the Labor Markets for Anesthesiology. Santa Monica, CA: Rand Corporation; 2010. http://www.rand.org/pubs/technical_reports/TR688.html. Accessed February 12, 2014.