Ian D. Coulter, PhD; Paul G. Shekelle, MD, PhD

A. Current and Projected Supply of Chiropractors

In 1970, there were an estimated 13,000 chiropractors licensed in the United States (Cooper, 1996). This number had increased to 40,000 in 1990 and to approximately 50,000 in 1994. Thus, there is roughly one chiropractor for every 5,000 U.S. residents. Estimates of the proportion of chiropractors who are in full-time practice range from 82 percent in a large national survey conducted in 1993 (Christensen) to 96 percent in a 1995 survey of members of the American Chiropractic Association (Goertz, 1996). Almost 90 percent of chiropractors report working at least 30 hours per week (Christensen, 1993) and the average chiropractor claims to work about 42 hours per week (Goertz, 1996). Estimates of the percentage of chiropractors in solo private practice range from 67 percent (Christensen, 1993) to 76 percent (Goertz, 1996), indicating that most chiropractors have remained in solo practice.

In 1995, there were 14,040 students enrolled in the 16 accredited chiropractic colleges, 2,864 of whom graduated in that year.³ The enrollment patterns in chiropractic colleges have been stable for the last several years with no new colleges being established since 1994. It appears that enrollments in chiropractic colleges are beginning to stabilize after a period of growth. However, with about 2,900 graduates per year, an increasing proportion of chiropractors is recent graduates.

A recent study estimated that the number of chiropractors will double by the year 2010 (to over 100,000), far exceeding the 16 percent increase projected for medical doctors (Cooper, 1996). This projection is based on two assumptions: (1) the number of chiropractor students will increase by 25 percent over the next 5 years and then stabilize and (2) 27 percent of currently active chiropractors will die or retire by 2010. Thus, it appears that chiropractors will represent a substantially larger proportion of health care professionals in the coming years.

B. Geographic Distribution

Colleges of chiropractic are not evenly distributed throughout the United States. Of the 16 accredited schools, 4 are in California, 2 in Texas, 2 in Missouri. The other eight are distributed in Oregon, Minnesota, Illinois, New York State, Georgia, Iowa, Connecticut, and South Carolina. Partly as a result of the distribution of the colleges, the practitioners are not evenly distributed throughout the states. Data from the Federation of Chiropractic Licensing Boards (FCLB) on the number of chiropractors licensed in each of the States in 1993 and 1995 (FCLB, 1996) are presented in Table IV-1. States with more than 3,000 chiropractors in 1995 were: California, New York, Florida, Pennsylvania, and Texas. Twenty-two States had more than 1,000 chiropractors. California, with 9,879 licensed chiropractors, had twice the number of the next largest state (New York).

The FCLB information, in conjunction with data on the estimated population in each state during these years, permitted estimation of the number of licensed chiropractors in each state per 100,000 population (Table 11). Because some chiropractors are licensed in more than one state and a substantial fraction is not practicing full-time (or at all), these numbers undoubtedly overestimate the supply of chiropractors. In addition, the dramatic differences in the reported number of chiropractors between 1993 and 1995 in some States (e.g., Hawaii, Illinois, New York, and Pennsylvania) casts further doubt on the accuracy of these data. Alternatively, changes in examination requirements, maintenance of inactive vs. active licenses and examination and license fees may account for year to year differences.

Nevertheless, the data are probably adequate for identifying States or at least regions that have particularly high or low population-to-chiropractor ratios. Specifically, States with the fewest chiropractors per 100,000 population in 1995 were: District of Columbia, Louisiana, Maryland, Mississippi, and West Virginia. The States with the most chiropractors per capita were: Arizona, Colorado, and Hawaii. It appears that States in the West have been generally more hospitable to chiropractors than those in the South and East. About 60 percent of chiropractors worked in urban or suburban communities, 35 percent in small towns, and 5 percent in rural areas (Goertz, 1996).

C. Utilization of Chiropractic Services

The proportion of the United States population that uses chiropractors and the number of chiropractic visits per capita have about doubled in the past 15-20 years. A 1980 national survey commissioned by the United States Department of Health, Education, and Welfare reported that 3.6 percent of the population used chiropractors that year and that there were 62 visits per 100 person-years (Von Kuster, 1980). The 1980 National Medical Care Utilization and Expenditure Survey found that 4 percent of the population saw a chiropractor (Mugge, 1984; Mugge, 1986). A community-based study of claims data collected between 1974 and 1982 reported that there were 41 chiropractic visits per 100 person-years (Shekelle, 1991). Each of the above studies also reported both large-area and small-area geographic variations in chiropractic use. More recently, a national telephone survey of the United States adult population reported that 7 percent of persons had used a chiropractor in the prior year (Eisenberg, 1993), and the chiropractic visit rate, as calculated from a recent cluster sample in 5 communities in the U.S., was 100 visits per 100 person-years (Hurwitz, in press). In this study, there were only small (less than 10 percent) differences in the estimated use rates among sites (San Diego, California; Portland, Oregon; Vancouver, Washington; Minneapolis-St. Paul, Minnesota; Miami, Florida).

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