HOSPITAL MERGERS AND MARKET OVERLAP

Objective. To address two questions: What are the characteristics of h ospitals that affect the likelihood of their being involved in a merge r? What characteristics of particular pairs of hospitals affect the li kelihood of the pair engaging in a merger? Data Sources/Study Setting. Hospitals in the 12-county region surrounding the San Francisco Bay d uring the period 1983 to 1992 were the focus of the study. Data were d rawn from secondary sources, including the Lexis/Nexis database, the A merican Hospital Association, and the Office of Statewide Health Plann ing and Development of the State of California. Study Design. Seventee n hospital mergers during the study period were identified. A random s ample of pairs of hospitals that did not merge was drawn to establish a statistically efficient control set. Models constructed from hypothe ses regarding hospital and market characteristics believed to be relat ed to merger likelihood were tested using logistic regression analysis . Data Collection. See Data Sources/Study Setting. Principal Findings. The analysis shows that the likelihood of a merger between a particul ar pair of hospitals is positively related to the degree of market ove rlap that exists between them. Furthermore, market overlap and perform ance difference interact in their effect on merger likelihood. In an a nalysis of individual hospitals, conditions of rivalry, hospital marke t share, and hospital size were not found to influence the likelihood that a hospital will engage in a merger. Conclusions. Mergers between hospitals are not driven directly by considerations of market power or efficiency as much as by the existence of specific merger opportuniti es in the hospitals' local markets. Market overlap is a condition that enables a merger to occur, but other factors, such as the relative pe rformance levels of the hospitals in question and their ownership and teaching status, also play a role in influencing the likelihood that a merger will in fact take place.