In addition, a growing number of centers (18-20%) are now run by medical facilities or doctor groups, who use or employ their own clinic and administrative staffs or utilize existing supplier centers to serve the employee population. Finally, an increasing number of companies are participating in shared, multi-employer clinics, located either on one company's location or centrally situated.The supplier will develop, staff and manage the center either at the request of a group of companies or will solicit companies in a defined geographical area. Regardless of the model used, it's key that company stay taken part in service provider choice, center oversight, tactical and policy direction. Staffing practices differ from one onsite clinic to another, though over 60% of centers are led by a Nurse Practitioner or Physician's Assistant.