Did Medicaid Expansion Deteriorate Access to Care for Privately Insured Patients?

Medicaid expansion under the Affordable Care Act (ACA) introduced many new patients to the health care system by extending eligibility for public health insurance coverage but did so without a corresponding increase in health care supply. Some policymakers remain concerned the ACA’s Medicaid expansions placed a strain on local health care systems because it was possible demand for health care grew faster than the local primary care workforce could adapt. We explore whether a gap between patient demand, prompted by the state’s Medicaid expansion, and provider capacity exists by examining the effect of Michigan’s Medicaid expansion on wait times for primary care appointment. In doing so, we use simulated patient (i.e. “secret shopper”) data on primary care clinics in Michigan. The data are longitudinal and allow for a provider-by-period fixed effects regression approach, and the periods of analysis include four months prior to Michigan’s Medicaid expansion, as well as four, eight, and twelve months after the expansion. Previous studies established that Medicaid coverage improves appointment availability for Medicaid patients, and we expand upon this work by testing for potentially negative spillover effects—increased difficulty of appointment availability and lengthened wait times due to “surges” in the demand for primary medical care among newly covered patients. First, we explore two alternative model specifications linking variation in appointment availability to growth in the market’s insured population and the timing of the expansion; results from both approaches find limited evidence to suggest difficulty in appointment scheduling for privately insured patients or Medicaid patients. In our third model specification, we specifically focus on the relationship between the size of the adult insured population—relative to the local (i.e. county-level) supply of primary care providers—and wait times for a scheduled primary care visit. We highlight this third specification as our preferred model because it considers the potential capacity of the local primary care workforce by examining the insured population-to-provider ratio. We find as the ratio of insured adults-to-primary care providers increases over time, scheduled appointment availability (0.002 percentage points [p>0.10] and wait times (-0.0082 percentage points [p>0.10]) were unaffected for privately insured patients—providing plausible evidence that access to primary care for privately insured patients had not eroded in response to Michigan’s Medicaid expansion.