The consequences of firm scope and scale on patient access to healthcare.

OBJECTIVE: The aim was to quantify changes in the market structure of primary care physicians and examine its relationship with access to care. DATA SOURCES AND STUDY SETTING: We created measures of market structure from a 5% sample of Medicare fee-for-service claims and examined access to care using nationally representative data from the Medical Expenditure Panel Survey (MEPS). Our study spanned from 2008 to 2019. STUDY DESIGN: We used a linear probability model to estimate the relationship between access to care and two measures of market structure: concentration, measured by the Herfindahl-Hirschman Index (HHI), and vertical integration, measured by the market share of multispecialty firms. Our model controlled for year and ZIP code fixed effects, respondents' demographics and health status, and other measures of market structure. DATA COLLECTION/EXTRACTION METHODS: All adult respondents in the MEPS were included. PRINCIPAL FINDINGS: The percentage of people living in concentrated ZIP codes (HHI above 1500) increased from 37% in 2008 to 53% in 2019. During the same period, the median market share of multispecialty firms rose from 30% to 48%. Respondents in highly concentrated ZIP codes (HHI over 2500) were 5.9 percentage points (95% CI: -1.4 to -10.4) less likely to report having access to immediate care than respondents in unconcentrated ZIP codes. The association was largest among Medicaid beneficiaries, a 17.3 percentage point reduction (95% CI: -5.1 to -29.4). When we applied a model that was robust to biases from treatments with staggered timing, the estimated association remained negative but was not statistically significant. We found no association between HHI and indicators for having a usual source of care and annual checkups. The multispecialty market share was negatively associated with checkups, but not other measures of access. CONCLUSIONS: Increases in concentration may reduce some types of access to healthcare. These effects appear most pronounced among Medicaid beneficiaries.

Physician Market Structure, Patient Outcomes, and Spending: An Examination of Medicare Beneficiaries.

OBJECTIVE: To understand the impact of changes in physician market structure on clinical outcomes and health care utilization. DATA SOURCES: 2005-2012 Medicare fee-for-service claims and enrollment data. STUDY DESIGN: We consider the effect of cardiology market structure on utilization and health outcomes for four patient populations. We estimate the risk-adjusted impact of competition using multivariate regression models. PRINCIPAL FINDINGS: The study finds that an increase in consolidation leads to statistically and economically significant increases in negative health outcomes. For example, we find that moving from a zip code at the 25th percentile of cardiology market concentration to one at the 75th percentile would be associated with 5 to 7 percent increases in risk-adjusted mortality for three of the sample populations. We also found higher expenditures in more concentrated markets. For example, moving from a zip code at the 25th percentile of cardiology market concentration to one at the 75th would be associated with 7 to 11 percent increases in expenditures, depending on sample population. CONCLUSIONS: Our estimates indicate that increases in cardiology market concentration are associated with worse health outcomes and higher health care expenditures. Some effects may be attributed to vertical as well as horizontal changes.

How vertical integration affects the quantity and cost of care for Medicare beneficiaries.

Health systems are employing physicians in growing numbers. The implications of this trend are poorly understood and controversial. We use rich data from the Centers for Medicare and Medicaid Services to examine the effects of a set of physician acquisitions by hospital systems on outpatient utilization and spending. We find that financial integration systematically produces economically large changes in the acquired physicians' behavior, but has less consistent effects at the acquiring system level.

The role of education in the production of health: an empirical analysis of smoking behavior.

We estimate the effect of education on smoking. Our estimation strategy "differences out" the impact of unobserved characteristics correlated with education by exploiting education differences between similarly selected groups 1 year apart in their life cycle. Individuals with a given age, education, and student status in the current and previous year are compared to their counterparts born 1 year later with the same age, education, and student status in the following and current year. We find that an additional year of education does not have a causal effect on smoking. Unobserved factors correlated with education entirely explain their cross-sectional relationship.