Determinants of physician assignment rates by type of service.

In this article, the determinants of physician assignment rates under the Medicare program are examined separately for medical, surgical, laboratory, and radiology services. Data for this study include copies of all Medicare claims submitted by over 1,200 Colorado general practitioners, internists, and general surgeons during the periods both before and after they experienced a substantial change in program reimbursement rates. The results indicate that there is a significant positive relationship between changes in reimbursement and changes in assignment rates for medical, laboratory, and radiology services, but the relationship for surgical service is not significant. Furthermore, for laboratory and radiology services, only the change in medical service reimbursement is significant--reimbursement rates for laboratory and radiology services are not.