Evidence for the Will Rogers phenomenon in migration of employees to managed care plans.

Employees have increasing opportunities to enroll in managed care plans, and employers tend to favor these plans because of their lower costs. However, lower costs may be the result of selection of healthier patients into managed care plans. This study measured differences in health care utilization across an indemnity plan and a managed care plan, and for all employees together. We found that apparent increases in utilization in both indemnity and managed care plans disappeared when the plans were viewed together, reflecting the migration of sicker patients from indemnity plans to managed care plans.