Graduation Year


Document Type




Degree Granting Department

Public Health

Major Professor

Russell Kirby Ph.D.

Committee Member

Roseanne Collins, Ph.D.

Committee Member

Charles Mahan M.D.

Committee Member

Thomas Mason Ph.D.

Committee Member

Kay Perrin Ph.D.

Committee Member

James Studnicki, Sc.D.


health care finance, hospital markets, index of competition, managed care penetration, managed care concentration, outcomes, surgical volume, selective contracting, health maintainence organization, hospital utilization, hospital market share



This study is designed to determine whether managed care has had an influence on the number and distribution of procedures with demonstrated volume and outcome endogeneity in Florida healthcare markets; in addition, methods are developed to determine which measures of managed care activity best predict the impact of managed care in health care markets.


A retrospective population based cohort design is used capitalizing on the variability among Florida markets between 1995 and 1999, a period which captured the full business life cycle of managed care plans statistical areas and competing hospitals (market share) over time. Multiple regression models were used to measure the impact of managed care activity (penetration, competition and concentration) on both the number of the selected procedures (volume) at the market and hospital level and the distribution of those procedures (hospital market share) controlling for socio-demographic and market factors known to influence surgical procedure utilization. Post hoc analysis of the procedure volume model was conducted using a log linear generalized estimating equation which permitted the use of all of the volume data over the study period to provide validation for the difference score methodology.

Key Findings

Procedures with demonstrated volume and outcome endogeneity increased over the period, and remained a consistent proportion of the total procedure volume. The procedure rate remained stable over the study period with substantial small area variation. Change in managed care concentration was consistently and negatively associated with procedure volume at both the MSA (β = -19.67; p = 0.0489) and hospital level (β = -4.088; p = 0.0027).Change in the total population and the number of specialty surgeons had a substantial, consistent and positive relationship to change in procedure volume at both the market and hospital level. The change in the index of competition was positively associated with change in hospital market share (β = 0.1005; p = 0.05); whereas, neither change in managed care penetration nor change in managed care IOC was predictive of change in procedure volume at the market level. The managed care variables were not correlated when difference scores were utilized providing evidence that the managed care variables measure different constructs and behave differently.


As markets for managed care become more concentrated, the number of surgical procedures with volume and outcome endogeneity declines; the specific reasons for the observed decline require additional study. Hospitals experience increases in market share for these procedures when the managed care markets are more competitive. Studies of managed care require consideration of the stage of managed care development in order to understand its influence and the use of difference scores as a method to measure change over time has substantial potential for the study of health care markets that are continually changing.