Financial Margin Dynamics After Hospital Chain-Joining: A Staggered DiD Event Study, 2014–2023

Project Description Title: Financial Margin Dynamics After Hospital Chain-Joining: A Staggered DiD Event Study, 2014–2023 Overview: This project investigates the financial implications of hospital chain affiliation in the United States using a robust staggered-adoption difference-in-differences (DiD) framework. Specifically, we assess whether hospitals that join multi-hospital systems (“chains”) experience systematic changes in financial performance—measured by total, operating, and cash flow margins—following sustained integration. Purpose: Consolidation in the U.S. hospital sector has accelerated over the past decade, often justified on the grounds of efficiency and financial sustainability. However, empirical evidence on whether chain affiliation improves hospital-level financial margins remains limited and mixed. This study aims to clarify whether chain joining leads to durable improvements in profitability, liquidity, or operational performance. Data: We use a RAND-processed national panel derived from Medicare Cost Reports (HCRIS), spanning short-term acute care hospitals from 2014 to 2023. The RAND version harmonizes variables and improves longitudinal tracking. Chain affiliation is defined via a standardized binary indicator derived from home-office cost reporting fields. Design & Methods: The analysis employs the Sun & Abraham (2020) interaction-weighted estimator for event studies with staggered treatment timing, which is robust to treatment-effect heterogeneity across cohorts. Our primary specifications include: Hospital and year fixed effects Hospital-clustered standard errors Outcome winsorization and ratio cleaning to address data artifacts Robustness checks include: Restriction to a balanced panel (hospitals observed 2014–2023) A placebo test among never-treated hospitals with random pseudo-treatment years A stacked event study re-centered around treatment year, with constructed controls. Heterogeneity analysis by ownership type (nonprofit vs. for-profit) Expected Outcomes: Our preliminary results indicate no consistent or significant improvement in financial margins following chain affiliation. Most dynamic effects are economically small and statistically insignificant. While some heterogeneity is observed (e.g., nonprofits may show longer-term margin gains), the overall findings suggest limited short-run financial benefit from chain joining, at least within the observed four-year post-entry window. Deliverables Included in this Repository: Stata replication code (.do file) Complete log file of analysis Clean event-study plots and exported coefficient tables README file with data access statement and instructions Data Access: Due to licensing restrictions, the RAND HCRIS hospital panel used in this study cannot be publicly redistributed. However, qualified researchers may request access directly from RAND. All code and outputs in this repository are sufficient to replicate the analysis once full access is obtained.