Saskatchewan tried user fees in the 1970's.  It had no impact of doctor's billing, which was the goal.  Doctors simply saw fee paying patient more often and the poor, especially children did without care.  Glen Back published this research in 1980  See Beck. R. G. & Horne, J. (1980) Utilization of Publicly Insured Health Services in Saskatchewan Before, During and After Co-payment.  Medical Care 18 787-806.