Tamara Beetham, PhD, MPH

Job market paper

Primary Care Clinician Supply, Market Structure, and Access in the US

Tamara Beetham, Jane M. Zhu, Nicholas S.J. King, and Michael L. Barnett

Under review

Paper available upon request

Wait times for a new Medicare appointment, across and within metropolitan areas

Mean wait time, by metropolitan area

Range across clinics within each area

0 50 100 150 200 Wait time (days) New York, NY Denver, CO St. Louis, MO Little Rock, AR Minneapolis, MN Phoenix, AZ Richmond, VA Albuquerque, NM Providence, RI Portland, ME 280 metropolitan areas, ordered by mean
Clinics with observed wait time 104080
Not called
Mean wait time (days) 102030405060
10th to 90th percentile
Area mean
Overall mean
In the map, each dot is a metropolitan area, color shows the mean wait time in days, and dot area reflects the number of clinics with an observed wait time. Hatched states require all-party consent to call recording and were not called. In the range chart, each column is a metropolitan area, ordered by mean wait time; bars span the area's 10th to 90th percentile across clinics, and the dashed line is the mean across all clinics. Clinic wait times are capped at the 99th percentile of the national distribution.

Abstract

There are concerns over a primary care clinician shortage leading to long wait times in the US. However, little is known about factors associated with longer wait times. We used AI voice agents to conduct a simulated-patient audit of 12,935 eligible primary care clinics in 280 metropolitan statistical areas (MSAs) covering 53% of the US population. The caller asked whether the clinic accepted new Medicare patients and the wait time until the soonest appointment. We estimated associations of wait time with clinician supply, parent organization (firm) market share of Medicare patients, and other clinic and population characteristics. Overall, 81% of clinics accepted new Medicare patients (mean wait time 31 days; 12 and 55 days in the 10th and 90th percentile MSAs). Wait times were longer in MSAs with more primary care clinicians per 100,000 residents (+2.2 days per SD; 95%CI, 0.04, 4.3) and shorter in MSAs with more residents in primary care shortage areas. Wait times were longer at clinics whose firm had a larger market share of patients (+6.9 days per SD; 95%CI, 5.2, 8.6), and shorter for clinics with more competing firms per 100,000 residents in their market (−4.3 days per SD; 95%CI, −6.3, −2.3). After adjustment, firm market share accounted for more explained variance than any other factor (23% vs. 3% for primary care clinicians per 100,000). Wait times for new primary care patients varied widely and were better explained by market organization than clinician supply.

JEL codes: I11, I18, J44, L11 Keywords: primary care access, audit study, wait times, market structure, clinician supply, Medicare, AI voice agents

Wait time by clinician supply and shortage-area designation

Clinician supply
20 30 40 50 255075100125 Primary care clinicians per 100,000 residents Mean wait time (days)

+2.2 days per SD (95% CI, 0.04 to 4.3)

Shortage-area designation
20 30 40 50 020406080100 Residents living in a shortage area (%) Mean wait time (days)

−1.4 days per SD (95% CI, −2.8 to −0.1)

Clinics with an observed wait time (n = 7,691) are ranked on each measure and split into 20 equal-count bins. Each point is a bin's mean wait time, and the line is a least-squares fit to the individual clinics, with its 95% confidence interval shaded and standard errors clustered by metropolitan area. Gray bars show the distribution of clinics. Shortage-area designation is the share of the metropolitan area's residents living in a designated tract. Clinics in areas with no residents in a shortage area share one value and fall in a single bin. Estimates are unadjusted, per standard deviation (SD), and the horizontal axis ends at the 99th percentile.

Wait time by firm market share and competing firms

Firm market share
20 30 40 50 0204060 Firm market share of Medicare patient volume (%) Mean wait time (days)

+6.9 days per SD (95% CI, 5.2 to 8.6)

Competing firms
20 30 40 50 5101520 Competing firms per 100,000 residents Mean wait time (days)

−4.3 days per SD (95% CI, −6.3 to −2.3)

Firm market share is the share of the metropolitan area's Medicare primary care patients seen by the firm that owns the clinic. Competing firms are the distinct firms with a primary care clinic in the metropolitan area, per 100,000 residents. Bins, fitted lines, confidence intervals, and estimates are as in the figure above.

Adjusted associations of clinic and market characteristics with wait time

SD shift Share of explained variance Local market characteristics Firm market share of Medicare patient volume 17.0 23% Cost of living index 5.6 10% Competing firms per 100,000 residents 3.9 7% Primary care clinicians per 100,000 residents 20.7 3% Clinic in a shortage area no to yes 2% Nurse practitioner full practice authority no to yes 1% Individual clinic characteristics Clinicians at the clinic ×2.3 11% Medicare patients per clinician 203.5 10% Advanced practice clinician available no to yes 6% Clinic physician share 34.5 5% Local population demographics Share aged 65 and over 3.3 11% Share uninsured 4.9 4% Share with bachelor's 8.2 4% Share non-white 17.2 2% Clinic in a rural area no to yes 1% −10−50+5+10 Adjusted difference in wait time (days)
Estimates are from one linear regression of wait time on all the characteristics shown, among the 7,691 clinics with an observed wait time, with standard errors clustered by metropolitan area. Bars are 95% confidence intervals, and filled markers are significant at the 5% level. Continuous characteristics are per one SD increase. The SD shift column gives that step in the characteristic's units, or the factor by which it multiplies a characteristic measured on a log scale. Indicators compare no with yes. The share of explained variance is from a Shapley decomposition of the model's R² (0.08).

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