Hamilton B, & Ho V, (2000)

‘Hospital Mergers and Acquisitions: Does Market Consolidation Harm Patients?’

Journal of Health Economics 19(5) pp. 767-791

Tests the hypothesis that quality of patient care declines after a hospital is merged or acquired.
Uses panel data on hospitals in California from 1991-95.

Mergers have not had a measurable impact on inpatient mortality, although the associated standard errors are large.
Readmission rates and early discharge increased in some cases.