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Health System Formations

Decent Essays

4. Methods
Data and Study Sample
This study examined whether the two health system formations analyzed in the previous essay, Health System A and Health System B, can pass the antitrust safety zone test for horizontal hospital mergers and acquisitions. The main data source for this essay is MarketScan® Commercial Claims and Encounters Database, which is a unique private insurance claims database that includes 23 million employees, dependents and retirees from around 100 large private employers (Adamson, Chang & Hansen, 2008). This study collected patient flow information from this detailed database, which includes patient and hospital characteristics. The AHA Annual Survey Database™ is another source used in this study. Comprehensive hospital …show more content…

The PSA for hospital A1 in 2003 included three zip code areas: Atlanta, Georgia (Zip 303 and 302), and North Metro Area, Georgia (ZIP 300). The PSA share of a hospital would be the hospital’s total admissions divided by the total admissions for all residents in the PSA. When merging parties share zip code areas for their PSAs, the PSA share for the newly merged health system should include total admissions for both merging parties for the PSA. Table 2 also shows the 2003 patient admission distribution of Hospital A2 across postal zip codes from the MarketScan dataset. The PSA for A2 hospital includes North Metro Area, Georgia (ZIP 300, 301, and 305), and Nashville, Tennessee (ZIP 307). The overlapping zip code between Hospital A1 and Hospital A2 is North Metro Area, Georgia ZIP …show more content…

The MarketScan database includes patient zip code information but it only covers a sub-sample of the total hospital admissions. This study used patient admission distribution from MarketScan as a proxy for actual patient admission distribution across zip code areas. Table A1 and A2 show the patient zip code distributions of Health System B. Figure A1 and A2 show PSA 3 for Hospital B1 and PSA 4 for Hospital B2.

Herfindahl–Hirschman Index
The Herfindahl-Hirschman Index (HHI), one of the most frequently used market concentration measures, defined as the sum of squared market shares of a firm in the relevant market (Rhoades, 1993). The Antitrust Agencies recommend HHI to assess market concentration of a market for antitrust analysis (Department of Justice and Federal Trade Commission, 1992). The HHI is calculated by

where N refers total number of hospitals in a market, and xi refers market share for a hospital i. Holding the market shares of other hospitals equal, the change in HHI when hospital j and k would merge into a health system is calculated

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