Agency for Healthcare Research and Quality, Center for Financing, Access, and Cost Trends, Rockville, Maryland, USA.
Federal Trade Commission, Bureau of Economics, Washington, DC, USA.
Health Serv Res. 2024 Apr;59(2):e14228. doi: 10.1111/1475-6773.14228. Epub 2023 Sep 26.
The aim was to quantify changes in the market structure of primary care physicians and examine its relationship with access to care.
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.
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.
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.
Increases in concentration may reduce some types of access to healthcare. These effects appear most pronounced among Medicaid beneficiaries.
旨在量化初级保健医生市场结构的变化，并研究其与医疗服务可及性的关系。
我们从医疗保险按服务收费（Fee-For-Service）索赔的 5%样本中创建了市场结构衡量标准，并使用来自医疗支出面板调查（MEPS）的全国代表性数据来检查医疗服务可及性。我们的研究跨越了 2008 年至 2019 年。
我们使用线性概率模型来估计医疗服务可及性与两种市场结构衡量标准之间的关系：通过赫芬达尔-赫希曼指数（HHI）衡量的集中程度和通过多专科公司市场份额衡量的垂直整合。我们的模型控制了年度和邮政编码固定效应、受访者的人口统计学和健康状况以及其他市场结构衡量标准。
数据收集/提取方法：所有 MEPS 中的成年受访者均包括在内。
居住在集中邮政编码（HHI 高于 1500）的人数比例从 2008 年的 37%增加到 2019 年的 53%。同期，多专科公司的中位数市场份额从 30%上升到 48%。居住在高度集中邮政编码（HHI 超过 2500）的受访者报告拥有即时医疗服务的可能性比居住在非集中邮政编码的受访者低 5.9 个百分点（95%置信区间：-1.4 至-10.4）。这种关联在医疗补助受益人中最大，减少了 17.3 个百分点（95%置信区间：-5.1 至-29.4）。当我们应用一种对具有交错时间处理的偏差具有稳健性的模型时，估计的关联仍然为负，但不具有统计学意义。我们没有发现 HHI 与通常医疗服务来源和年度体检的指标之间存在关联。多专科市场份额与体检呈负相关，但与其他医疗服务可及性指标无关。
集中程度的增加可能会降低某些类型的医疗服务可及性。这些影响在医疗补助受益人中最为明显。
