The Effect of Provider Diversity on Racial Health Disparities: Evidence from the Military

This paper asks whether racial concordance between patients and medical providers — specifically, whether Black patients are treated by Black physicians — improves use of preventive care and reduces mortality among patients with chronic, manageable diseases. The authors argue that trust and communication deficits along racial lines cause Black patients to underuse low-cost, life-saving preventive care, and that increasing the share of Black providers addresses this deficit.

The authors use data from the Military Health System (MHS) Data Repository covering fiscal years 2003–2013, encompassing roughly 9.6 million beneficiaries. A distinctive feature of the MHS is that active-duty providers are themselves MHS beneficiaries, so their race is observed in the same eligibility files used for patients — overcoming the typical absence of provider-race data in claims databases. The study focuses on four chronic, deadly but manageable conditions: diabetes, hypertension, hypercholesterolemia, and clinical atherosclerotic cardiovascular disease. Preventive care is measured by medication fill-days for condition-appropriate generic drugs, HEDIS-recommended Comprehensive Diabetes Care compliance, and (for a subset) blood pressure control. Mortality is tracked across the full sample period.

The identification strategy exploits quasi-random variation in provider racial composition induced by across-base moves. The MHS setting generates abundant moves driven by DoD personnel management needs — not by patient health or preferences. Using a movers-only differences specification (analogous to Finkelstein et al. 2016), the authors compare differential changes in outcomes for Black versus non-Black patients who move to bases with larger versus smaller increases in the share of Black providers. This design includes fixed effects for both sending and receiving bases, controlling flexibly for regional quality differences. The estimand is an intent-to-treat effect among patients living within 10 miles of a base (who use on-base care 66% of the time).

The findings are consistent across all four disease samples. For diabetes, a move-induced one-standard-deviation increase in the share of Black diabetes providers is associated with a roughly 6 additional metformin fill-days per year (approximately 16% relative to the mean) and a 3 percentage-point increase (roughly 8% relative to the mean) in Comprehensive Diabetes Care compliance for Black relative to non-Black patients. Mortality falls by 0.4 percentage points — a 33% relative decline — for Black relative to non-Black diabetes patients following such a move.

Pooling across all four chronic-disease samples, a one-standard-deviation move-induced increase in the Black provider share is associated with approximately 3 additional fill-days of relevant preventive medication and a roughly 0.2 percentage-point reduction in mortality — approximately 15% relative to the mean mortality rate — for Black relative to non-Black patients.

A decomposition analysis combining the paper’s estimates with medical-literature parameters on the mortality effects of preventive medications finds that between 55% and 69% of the concordance mortality effect across the four disease samples can be attributed to improved medication adherence alone, with the remainder attributed to other aspects of the provider-patient relationship (e.g., lifestyle effects, other preventive care).

Scope conditions: results are local to MHS movers, who are on average slightly younger and healthier than non-movers, potentially understating concordance benefits for the full population. The MHS covers over 3% of all Black U.S. residents, but beneficiaries may differ from the general population. The paper measures Black patient / Black provider concordance specifically; it does not establish a symmetric concordance effect for non-Black patients. The concordance effect estimated is relative — it captures how much Black patients benefit more than non-Black patients from moving to a higher Black-provider-share base. A system-wide spillover mechanism (non-Black providers improving care for Black patients when working alongside more Black providers) cannot be ruled out and would also be consistent with the core concordance motivation.

Q: What is the central research question and why is the MHS an advantageous setting? A: The paper asks whether racial concordance between providers and patients causes Black patients to use more preventive care and achieve better health outcomes, focusing on the trust and communication channel. The MHS is advantageous because active-duty providers are themselves MHS beneficiaries, making their race observable — a feature absent in most claims databases. Across-base moves are driven by DoD staffing needs rather than patient health or preferences, providing quasi-random variation in provider racial composition. The system offers complete claims data covering both on- and off-base care, allowing full mortality tracking.

Q: How does the empirical strategy address selection concerns that plague prior concordance studies? A: Prior studies face selection problems from Black patients choosing different doctors than white patients and from residential segregation concentrating Black patients and Black physicians in regions with distinct care quality. The movers-based differences specification directly addresses both problems: it uses only patients who move across bases, comparing how the same individual’s outcomes change relative to non-Black patients experiencing the same move, as a function of the move-induced change in the Black provider share. Inclusion of fixed effects for both sending and receiving bases accounts flexibly for regional quality differences. Balance tests on observable patient characteristics show no differential sorting of Black versus non-Black patients toward high-Black-provider-share bases.

Q: What specific preventive care and outcome measures are used for each disease? A: For diabetes, the primary measures are annual metformin fill-days and Comprehensive Diabetes Care (CDC) compliance — defined as receiving HbA1c testing, a retinal eye exam, and medical attention for nephropathy in the focal year — plus blood pressure control (available only from 2009 onward for on-base patients). For hypertension, the measures are annual fill-days of WHO-recommended antihypertensives (thiazides, ACEs/ARBs, or long-acting dihydropyridine CCBs) and blood pressure control. For hypercholesterolemia, the measure is fill-days of antilipemic agents, bile acid sequestrants, and statins. For atherosclerotic cardiovascular disease, the HEDIS statin therapy receipt indicator is used. Mortality is tracked across all four samples.

Q: What are the main quantitative results for the diabetes sample? A: A move-induced one-standard-deviation increase in the share of Black diabetes providers is associated with approximately 6 additional metformin fill-days annually for Black relative to non-Black patients (roughly 16% relative to the mean). Compliance with Comprehensive Diabetes Care increases by 3 percentage points for Black relative to non-Black patients (roughly 8% relative to the mean). Mortality falls by 0.4 percentage points for Black relative to non-Black patients — a 33% relative decline — in connection with the same one-standard-deviation increase in Black provider share.

Q: What are the pooled results across all four chronic-disease samples? A: Pooling across diabetes, hypertension, hypercholesterolemia, and atherosclerotic cardiovascular disease, a one-standard-deviation move-induced increase in the Black provider share is associated with approximately 3 additional preventive medication fill-days per year for Black relative to non-Black patients. The pooled mortality effect is a 0.2 percentage-point reduction — roughly 15% relative to the mean mortality rate — for Black relative to non-Black patients.

Q: How much of the concordance mortality effect operates through medication adherence? A: The decomposition combines the paper’s estimated concordance effects on medication fill-days with medical-literature estimates of the mortality impact of each additional fill-day. For the diabetes sample, increased metformin adherence (4.2 additional fill-days) explains approximately 58.8% of the 0.4 percentage-point concordance mortality effect, with the residual 41.2% attributed to other channels such as lifestyle changes or other preventive care. Across all four disease samples, the medication fill-day channel explains between 55% and 69% of the respective concordance mortality effects.

Q: What specification checks do the authors conduct to validate causal identification? A: The authors conduct five main checks. First, balance regressions show that move-induced changes in Black provider share are not differentially related to baseline patient characteristics for Black versus non-Black patients. Second, regressions of the probability of moving on initial Black provider share and its interaction with patient race yield a near-zero concordance coefficient (0.008, SE 0.023), indicating no differential sorting. Third, regressions of post-move on-base care share on the concordance interaction term yield a near-zero coefficient (0.002, SE 0.003), indicating no differential race-specific selection into on-base care. Fourth, a distance falsification test shows that concordance coefficients are near zero and statistically insignificant for patients living more than 10 miles from the base. Fifth, event-study dynamics show no pre-move divergence in preventive care adherence between Black and non-Black patients, with a positive divergence emerging only after the move to a higher Black-provider-share base.

Q: How does the paper separate a concordance effect from a pure Black-physician-quality effect? A: The paper estimates a “first stage” specification on the subsample receiving on-base care (where provider race is observed), regressing the change in the probability of visiting a Black provider on the move-induced change in Black provider density. The results show an approximately one-to-one relationship between higher Black provider availability and increased visits to Black providers for all patients, with only a modest differential by patient race. This confirms that non-Black patients also see more Black providers when Black provider density rises, allowing the interaction specification to isolate concordance from a pure physician-quality effect.

Q: How do the authors assess the potential role of spillover effects? A: The authors acknowledge they cannot rule out that some of the estimated concordance effect arises through system-wide spillovers — for instance, non-Black providers on bases with more Black colleagues may improve their care for Black patients through peer learning or information transmission. They note that even if such a spillover mechanism operates, it is still consistent with the paper’s core concordance motivation, because provider-knowledge deficiencies about treating Black patients are among the theorized channels of racial discordance.

Q: What do the results imply for the overall racial mortality gap? A: Among MHS beneficiaries aged 20–65, Black beneficiaries are roughly 38% more likely to have diabetes and die over the sample period than non-Black beneficiaries; this gap appears driven primarily by higher diabetes prevalence rather than a within-diabetes mortality gap. Applying the diabetes concordance mortality estimate (a 0.4 percentage-point reduction), the authors calculate that a one-standard-deviation increase in the Black provider share would reduce the overall diabetes mortality gap from 38% to approximately 21% — a substantial narrowing driven by the concordance effect operating through conditional-on-prevalence outcomes.

Q: What are the policy implications of the findings? A: The results imply that investments in increasing physician workforce diversity could meaningfully reduce racial mortality disparities in the United States, particularly for chronic diseases manageable through preventive medication. The paper notes the results are relevant to affirmative action policies in medical school admissions, specifically the pending Supreme Court cases Students for Fair Admissions v. University of North Carolina and Students for Fair Admissions v. Harvard at the time of writing. The MHS population covered in the study includes over 3% of all Black U.S. residents, so the policy stakes extend substantially beyond the military context.

Q: What are the limitations of the study regarding generalizability? A: Movers in the chronic-disease samples are on average about four years younger and 0.2 percentage points less likely to die than non-movers, suggesting the local average treatment effect for movers may understate concordance benefits for the full population. The MHS population may be healthier overall than the general population, though conditioning on chronic-disease patients mitigates this concern. The paper covers only Black-patient/Black-provider concordance; concordance effects for other racial and ethnic groups are not estimated. The estimate of the concordance coefficient technically captures how much the Black patient / Black provider concordance effect exceeds the non-Black patient / non-Black provider concordance effect, meaning the absolute magnitude of Black concordance benefits is understated if non-Black concordance effects are also positive.

Racial concordance: In this paper’s usage, the match between the race of a patient and their treating physician — specifically Black patient / Black provider pairing — theorized to improve care through trust, communication, and reduced provider knowledge deficiencies about Black patients.

Provider Black share: The fraction of outpatient office visits for a given chronic condition at a given military base that are attended by Black active-duty providers, used as the base-level treatment variable; varies across bases from zero to approximately 20 percentage points in the pooled sample.

Movers-based differences specification: An identification strategy that restricts to patients who relocate across military bases exactly once during the sample period and estimates the differential change in outcomes for Black versus non-Black patients as a function of the move-induced change in the base’s Black provider share, including fixed effects for both the sending and receiving base.

Intent-to-treat (ITT) effect: The concordance estimate as applied to all patients living within 10 miles of a base — regardless of whether they actually received on-base care — to avoid selection bias from differential race-specific decisions to seek care on versus off base.

Comprehensive Diabetes Care (CDC): A HEDIS composite measure requiring receipt of all three of the following in the focal year: HbA1c testing, a retinal eye exam, and medical attention for nephropathy (via microalbumin exam, ACE/ARB therapy, or nephropathy treatment).

Medication fill-days: Annual days of supply dispensed for condition-appropriate generic medications (metformin for diabetes; thiazides/ACEs/ARBs/CCBs for hypertension; antilipemic agents, bile acid sequestrants, and statins for hypercholesterolemia; statins for atherosclerotic cardiovascular disease), used as the primary preventive care adherence measure.

Decomposition of concordance mortality effect: A calculation that uses the paper’s estimated concordance effect on medication fill-days, combined with medical-literature estimates of the mortality impact per fill-day, to determine what share of the total concordance mortality effect passes through medication adherence versus other channels (lifestyle, other preventive care).