Do HMOs make a difference? Use of health services

This study analyzes the effects of health maintenance organization (HMOs) o n the use of health services by the privately, insured, nonelderly populati on. After controlling for population and location differences, HMOs increas e physician visits, nonphysician practitioner visits, ann total ambulatory visits by modest but significant margins girls, while shifting the mix of p hysician care front specialists to primary care physicians. HMOs also incre ase use of two preventive services: mammography screening and flu shots. Co ntrary to expectation, however, the study finds no significant differences between HMO and non-HMO enrollees in the rise of hospital, surgery, and eme rgency room services.